A gas-burning pizza oven

Abstract

A gas-burning pizza oven (100, fig.1A) comprising an oven cavity 120 at the front of the oven with an access port (110, fig.1A), a baking stone 126 and at least one elongate gas burner 128a having one or more apertures (150, fig.4) for gas egress, whereby the total aperture area of the one or more aperture(s) per unit length varies along the length of the elongate gas burner (fig.4). Also disclosed are embodiments whereby in the oven with an open front cavity; the elongate burner 128a extends from the front to the back of the oven, the burner providing less heat at the rear than the front (claim 8); two elongate burners 128a, 128b extending from the front to the back of the oven, and are on opposite sides of the cooking space (claim 23); and the oven having greater width than depth and a heater extending down each side of the oven cavity 120 (claim 28).

Description

Field of the invention The present invention relates to a gas-burning pizza oven. Background to the invention It is known to provide pizza ovens which are heated using gas burners. Furthermore, it is common to provide pizza ovens with an open access port through which a pizza to be cooked may be placed inside the oven and through which a pizza which has been cooked in the oven may be removed from the oven. An open access port in a pizza oven may result in a cooling effect near the oven entrance due to air from the surrounding atmosphere entering the oven. This can be undesirable as it may lead to uneven cooking temperatures within the oven. In particular the temperature of the baking stone on which a pizza is cooked in the oven may be lower at the front of the oven cavity than at the middle and rear. This can significantly affect pizza quality. Some embodiments of the invention seek to address these issues. Some embodiments address widthwise variation in pizza stone temperature. Pizza ovens with gas burners and at least partially open access ports typically have gas burners at the back of the oven, opposite the access port. They are significantly deeper than 22 they are wide. It is understood in the field that this arrangement reduces heat loss through the access port. Nevertheless, we have found that this arrangement promotes uneven heating and lacks flexibility. Some embodiments of the invention address these issues. Summary of the invention In accordance with a first aspect of the present invention, there is provided a gas-burning pizza oven comprising: an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the gas-burning pizza oven; at least one elongate gas burner, extending in a direction within the oven cavity from a back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven; whereby the at least one elongate gas burner is configured to provide less heating power to the oven cavity at a rearward combustion region of the at least one gas burner than at a frontward combustion region of the at least one gas burner. The at least one gas burner is configured to provide less heating power to the oven cavity at a rearward combustion region of the at least one gas burner than at a frontward combustion region of the at least one gas burner. This configuration reduces (minimises) the temperature variation between the frontward region and rearward region, compared to an oven which is heated conventionally, for example with a constant heating power along the oven sides, or only from the back of the oven. This promotes an even cooking temperature, for example oven temperature, or baking stone temperature, or oven temperature and baking stone temperature. This configuration mitigates the problem of heat escape through the access port leading to an uneven temperature in the oven cavity including an uneven temperature of the base. An uneven temperature is undesirable as it results in unevenly cooked food. By a combustion region we refer to a region of the at least one gas burner where combustion takes place. The frontward combustion region of the at least one gas burner is located in front of the rearward combustion region of the at least one gas burner. Typically, the frontward combustion region of the at least one gas burner is in the front half, or front quarter, of the oven cavity. The frontward region need not comprise the front end of the at least one gas burner. Typically, the rearward combustion region of the at least one gas burner is in the back half, or back quarter, of the oven cavity. The rearward combustion region may, or may not, comprise the back end of the at least one gas burner. There can be substantial benefits to reducing heat variation over much of the depth of a baking stone whilst still allowing variation at the absolute front and / or back of the baking stone, as these regions are used less than the centre of the baking stone during cooking. Thus, there may be a further combustion region of the at least one gas burner, rearward of the rearward combustion region, which is configured to provide more heating power to the oven cavity than at the rearward combustion region. Thus, although the rearward combustion region is rearward of the frontward combustion region, it may be that it is not the rearmost combustion region. The frontward combustion region of the at least one gas burner is typically positioned closer to the access port than is the rearward combustion region of the at least one gas burner. The position of the frontward combustion region of the at least one gas burner typically corresponds to the position of a maximum in the heating power of the gas burner. The position of the rearward combustion region of the at least one gas burner typically corresponds to the position of a minimum in the heating power of the gas burner. The frontward region of the gas burner may have a length (measured from the back to the front of the oven cavity) of at least 10% of the length of the oven cavity. The rearward region of the gas burner may have a length of at least 10% of the length of the oven cavity. The frontward combustion region of the at least one gas burner is typically not at the position of the access port. The rearward combustion region of the at least one gas burner may be not at the furthest point within the oven cavity from the access port. By the front end of the gas-burning pizza oven, and of the oven cavity, we refer to the part closest to the access port and by the back end we refer to the part furthest from the access port. By the combustion region of a gas burner we refer to the longitudinal extent of the gas burner where combustion takes place in use. It is not relevant whether or not there is a noncombustion region at the rear end of, or behind, the gas burner. By heating power we refer to the power of heat generated by combustion per unit length of a gas burner. The oven cavity may be bounded by an enclosing wall or walls. For example, the gas-burning pizza oven may comprise a base. The base may define the bottom of the oven cavity. The base may be suitable for the placement thereupon of a baking stone. The baking stone may provide a surface upon which an item such as a pizza is cooked in the apparatus. The oven cavity may be bounded by an enclosing dome. The enclosing dome may form a ceiling. The oven cavity may be bounded by an enclosing dome and a base. The structure of the enclosing dome may be such that space is available for the access port of the gasburning pizza oven. A cooking space may be present within the oven cavity. The cooking space may be the space within which food is cooked in the oven. The cooking space may be an area, for example of the base, upon which food is cooked. The cooking space may be provided by the baking stone. The cooking space may be trapezoidal, typically an isosceles trapezoid. The gas burner extends in a direction within the oven cavity from a back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven. The oven cavity may have an elongate footprint. For example, the base may be elongate. It will be understood that an elongate base has a length (e.g. a length may be a dimension defined by the extent of the base from the back of the oven cavity towards the access port) that is greater than its width (e.g. a width may be a dimension defined by the extent of the base in a direction parallel to the upper surface of the base and orthogonal to the length of the base). The base may be rectangular. The oven cavity may have a footprint which is elongate. For example, the base may be trapezoidal, typically isosceles trapezoidal. The base may be rectangular. The baking stone may be trapezoidal, typically isosceles trapezoidal, typically with a width which increases from the back end of the gas-burning pizza oven to the front end of the gas-burning pizza oven. The baking stone may be rectangular. The oven cavity may have a width which increases from the back end of the gas-burning pizza oven towards the front end of the gasburning pizza oven. The cooking space may have a width which increases from the back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven. The baking stone may have a width which increases from the back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven. It may be that there are first and second elongate gas burners. It may be that the distance between the first and second elongate gas burners increases from the back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven. The invention is especially beneficial in these cases, as the increasing distance between burners towards the front end of the gas-burning pizza oven would otherwise lead to a significant drop in temperature, particularly of the base, towards the front of the oven, if the heating power was constant along the length of each heating element. The increasing distance between burners towards the front end of the gas-burning pizza oven can make access easier. A back end of the gas-burning pizza oven typically runs along a side of a rectangular or isosceles trapezoidal base which is opposite to a side where the access port of the apparatus is located. An elongate gas burner may extend in a direction perpendicular to the side of the rectangular base along which the back end of the gas-burning pizza oven runs. An elongate gas burner may extend in a direction parallel to the side of the base extending from the back end of the gas-burning pizza oven to the front end of the oven. An elongate gas burner may be contained within the oven cavity. An elongate gas burner may extend from within 15%, within 10% or within 5% of the length (from back to front) of the oven cavity of the back of the oven cavity. An elongate gas burner may extend to within 15%, within 10% or within 5% of the length (from back to front) of the oven cavity of the front of the oven cavity. The pizza oven may be a portable pizza oven. The at least one gas burner may comprise a first elongate gas burner. Said first elongate gas burner may extend in a direction within the oven cavity from a back end of the oven cavity towards a front end of the oven cavity. The at least one gas burner may comprise a first elongate gas burner and a second elongate gas burner. It may be that each of the first elongate gas burner and second elongate gas burner extends in a direction within the oven cavity from a back end of the oven cavity towards a front end of the oven cavity. It may be that each of the first elongate gas burner and the second elongate gas burner are on opposite sides of the cooking space. It may be that each of the first elongate gas burner and the second elongate gas burner are adjacent opposite sides of the oven cavity. It may be that each of the first elongate gas burner and the second elongate gas burner are on opposite sides of the baking stone. It may be that there is no gas burner having a combustion region across the back end of the oven cavity, opposite the access port. It may be that there is no gas burner having a combustion region between the back end of the first elongate gas burner and the back end of the second elongate gas burner. The first elongate gas burner may extend in a direction within the oven cavity from a back end of the oven cavity towards a front end of the oven cavity at a first side of the oven. The second elongate gas burner may extend in a direction within the oven cavity from a back end of the oven cavity towards a front end of the oven cavity at a second side of the oven, opposite the first side. The cooking space may be positioned between the first elongate gas burner and the second elongate gas burner. A baking stone may be positioned between the first elongate gas burner and the second elongate gas burner. The first elongate gas burner and the second elongate gas burner may be positioned above the cooking surface of the baking stone. The distance between the first elongate gas burner and the second elongate gas burner may increase from the from back end of the oven cavity towards the front end of the oven cavity. Each elongate gas burner may be straight, extending in a direction within the oven cavity from the back end of the oven cavity towards the front end of the oven cavity directly. Each elongate gas burner may be curved, extending in a direction within the oven cavity from the back end of the oven cavity towards the front end of the oven cavity indirectly. Each elongate gas burner may be angled, extending in a direction within the oven cavity from the back end of the oven cavity towards the front end of the oven cavity with an angular change of direction along the length of the burner. It may be that the distance between the middle of the combustion region of the first elongate gas burner, and the middle of the combustion region of the second elongate gas burner, across the breadth of the oven cavity, is greater than the depth of the combustion region of either of the first or second elongate gas burners, measured in a direction from the access port to the opposite back of the oven cavity. It may be that the shortest distance between the combustion regions of the first and second elongate gas burners is greater than the length of the combustion regions of either of the first or second elongate gas burners. It may be that the average width of the cooking space is greater than the average depth of the cooking space. It may be that the average width of the baking stone is greater than the average depth of the backing stone. By depth we refer to extent in the direction from the access port to the back of the oven and by width we refer to the extent in the direction parallel to the breadth of the access port. Each elongate gas burner may comprise a lower upward extending portion and an upper portion which is angled inwards, towards the cooking space, relative to the lower portion. This arrangement angles the flames inwards and may improve air flow, especially when the roof of the oven cavity is dome shaped. The first elongate gas burner may be connected to the second elongate gas burner. The first elongate gas burner may be fluidically connected to the second elongate gas burner, so that gas fuel may be provided through a single inlet to each of the first elongate gas burner and the second elongate gas burner. The gas-burning pizza oven may comprise an inlet to supply gas fuel to the at least one elongate gas burner. The inlet may be positioned at a back end of the at least one elongate gas burner. The inlet may supply gas fuel to the first elongate gas burner and to the second elongate gas burner. The gas-burning pizza oven may comprise a gas supply path. The gas supply path may be arranged to supply a flow of gas fuel from one end of the at least one elongate gas burner to the other end of the at least one elongate gas burner. The gas supply path may be arranged to supply a flow of gas fuel from a back end of the at least one elongate gas burner to a front end of the at least one elongate gas burner. The gas supply path may be arranged to supply a flow of gas fuel to an intermediate region from which gas flows towards both the back and front ends of the at least one elongate gas burner. The gas supply path may be defined by one or more conduits. A consistent pressure of gas may thereby be maintained within the gas supply. Thus, the amount of gas combusted in a given length of the at least one gas burner is determined by the one or more apertures therein. Typically, a manual control is provided which regulates the flow of gas to both the first and second elongate gas burners. However, in some embodiments, individual first and second manual controls are provided to independently regulate the flow of gas to the first and second elongate gas burners. The one or more gas burners may each comprise one or more pipes for receiving gas for combustion. The first elongate gas burner may comprise one or more apertures distributed along its length. The second elongate gas burner may comprise one or more apertures distributed along its length. Each of the at least one elongate gas burners may comprise one or more (typically a plurality of) apertures distributed along its length. Gas fuel which is supplied to the elongate gas burner or burners passes through the burner within the burner and exits the burner through the one or more apertures. The gas fuel exiting the one of more apertures is combusted, producing a flame from each aperture. The flame or flames heat the pizza oven. The flame or flames which heat the oven are in this way controllable through selection of the aperture distribution. The total aperture area per unit length of elongate gas burner may increase from the rearward combustion region of the at least one gas burner to the frontward combustion region of the at least one gas burner. The total aperture area per unit length of elongate gas burner may increase from the back end of the gas burner combustion region to the front end of the gas burner combustion region. The increase may be tapered. The total aperture area per unit length of elongate gas burner may be the sum of the areas of the one or more apertures within a unit of length of the elongate gas burner. An aperture size or cross-section may increase in a tapered manner from the rearward combustion region of the at least one gas burner to the frontward combustion region of the at least one gas burner. An aperture size or cross-section may increase in a tapered manner from the back end of the gas burner combustion region to the front end of the gas burner combustion region. For example, the size or cross-section of individual apertures may increase in a tapered manner, for example in a steadily increasing manner, from the back end of the gas burner combustion region to the front end of the gas burner combustion region. The aperture size or cross-section may increase in a tapered manner from the back end of the gas burner combustion region to the front end of the gas burner combustion region through the number of apertures per unit length (referred to herein also as the density of apertures), for example apertures of uniform size, increasing in a tapered manner from the back end of the gas burner combustion region to the front end of the gas burner combustion region. The density of apertures may be the number of apertures per unit length of elongate gas burner. It may be that the number of apertures per unit length of elongate gas burner increases from the rearward combustion region of the at least one gas burner to the frontward combustion region of the at least one gas burner. It may be that the number of apertures per unit length of elongate gas burner increases from the end of the gas burner proximate the back end of the oven cavity to the end proximate the front end of the oven cavity. It may be that the number of apertures per unit length of elongate gas burner increases in a tapered manner, for example in a steadily increasing manner, from the end of the gas burner proximate the back end of the oven cavity to the end proximate the front end of the oven cavity. It may be that the aperture size is greater in the frontward region than in the rearward region. An aperture size may increase from the end of the gas burner proximate the back end of the oven cavity to the end proximate the front end of the oven cavity. The aperture size may be the total aperture area per unit area of burner. The aperture size may be the absolute size of an aperture. The aperture size may be the aperture diameter, or the aperture width, or the aperture length. The apertures may increase in size from the end of the gas burner proximate the back end of the oven cavity to the end proximate the front end of the oven cavity. If there is a further combustion region of the at least one gas burner, rearward of the rearward combustion region, which is configured to provide more heating power to the oven cavity than at the rearward combustion region, the total aperture area per unit length may increase from the rearward combustion region to the further combustion region, for example due to one or more of the number or the cross sectional area of apertures increasing, optionally in a tapered manner. Each aperture may have a circular form. Each aperture may have an oval form. Each aperture may be elongate in a length direction, parallel to the length of the gas burner in which the aperture is present. Each aperture may be elongate in a width direction, perpendicular to the length of the gas burner in which the aperture is present. Each aperture may have the form of a slot. The slot may be elongate lengthwise along the respective gas burner. An aperture in the form of a slot produces an elongate flame shape, contributing to even heating. It may be that the or each of the at least one elongate gas burner comprises a single elongate slot. The mean width of the slot may be less in the rearward region than the frontward region. This configuration causes there to be less heating power produced in the rearward region than the frontward region. An elongate slot may be tapered. It may be that the at least one elongate gas burner comprises a plurality of slots. The plurality of slots may be tapered. For example, a slot may have a width which is increased over the width of the neighbouring slot positioned closer to the back end of the oven. Each slot may have a width which is increased over the width of the neighbouring slot positioned closer to the back end of the oven. The increase in width promotes supply of fuel to the oven cavity and provides for a supply of gas to be combusted that increases steadily along the length of the at least one elongate gas burner. Enabling greater combustion of fuel at a frontward combustion region of the at least one gas burner than at a rearward combustion region of the at least one gas burner supports the maintenance of an even temperature gradient from the back end of the oven cavity to the front end of the oven cavity. The gas-burning pizza oven may comprise an oven cavity ceiling. The said gas burner may be arranged to produce a flame which follows a form of the oven cavity ceiling internal to the oven cavity. The oven cavity ceiling serves to maintain heat within the oven cavity. The gas-burning pizza oven may comprise an elongate protector. An elongate protector may extend along the length of each of the at least one elongate gas burner. An elongate protector may be situated between the flame produced by the gas burner and the cooking space, for example the baking stone. An elongate protector may comprise a shield. An elongate protector may comprise a shield which extends upwards from the base of the oven cavity. An elongate protector may provide a shield between food on the cooking surface and the flame produced by the gas burner. An elongate protector prevents food being cooked from singeing by flames from the gas burner. The elongate protector may help to form the flame shape. A first elongate protector may extend along the length of the first elongate gas burner. The first elongate protector may be situated between the flame produced by the first elongate gas burner and the cooking space, for example the baking stone. A second elongate protector may extend along the length of the second elongate gas burner. The second elongate protector may be situated between the flame produced by the second elongate gas burner and the cooking space, for example the baking stone. The cooking space, for example the baking stone, may be positioned between the first elongate protector and the second elongate protector. The gas burner may comprise a first elongate gas burner and a second elongate gas burner, wherein each of the first elongate gas burner and the second elongate gas burner extends in a direction within the oven cavity from a back end of the oven cavity towards a front end of the oven cavity. The oven cavity typically further comprises an air vent (which may be a primary air vent) to receive air for combustion. Typically, the (primary) air vent is in gaseous communication with the gas burner. Typically, the (primary) air vent is connected to the gas supply path. Thus, air received through the (primary) air vent is typically mixed with received gas to support combustion. It will be understood that an airvent is a vent other than the access port Typically, any air received through the access port in use is not used for (primary) combustion. The oven may comprise a (secondary) air vent. The (secondary) air vent may be to provide additional air to the flame generated by the combustion of a mixture of received gas and air received through the air vent in gaseous communication with the gas burner. A (secondary) air vent may be elongate and run along the length of a gas burner. The (secondary) air vent may be elongate and run along the length of the gas burner. The (secondary) air vent may run between the gas burner and the wall of the oven cavity proximate the gas burner. The (secondary) air vent may run underneath the gas burner. The (secondary) air vent may be configured to direct received air to pass between the gas burner and the wall of the oven cavity in preference to passing on the opposite (inwards) side of the gas burner. The (secondary) air vent may be elongate and run along the length of the gas burner between the gas burner and the elongate protector. The (secondary) air vent may be elongate, it may run along the length of the gas burner between the gas burner and the wall of the oven cavity proximate the gas burner. An elongate (secondary) air vent may also run along the length of the gas burner between the gas burner and the elongate protector. The first elongate gas burner may have an associated (secondary) air vent, being a first (secondary) air vent. The second elongate gas burner may have an associated (secondary) air vent, being a second (secondary) air vent The (secondary) air vent may comprise a series of vents. The series of vents may be aligned with each other, forming a vent which runs along the length of the gas burner. It may be that air received through the access port in use can support secondary combustion. Enabling the flame to access secondary air through a secondary airvent, enables the desired flame profile to be established from the very beginning of heating up the oven. Enabling the flame to access secondary air through a secondary air vent also allows a cleaner burn. Secondary air entering the oven cavity via the (secondary) air vent between the gas burner and the wall of the oven cavity proximate the gas burner and also between the gas burner and the elongate protector may provide a sheath air flow around the flame. The sheath air flow may assist in shaping the flame around the inside of the ceiling of the oven cavity. The elongate protector may extend in a direction away from the base of the oven cavity in such a way that a flow passage is formed between the elongate protector and the elongate gas burner. Secondary air entering the oven cavity via the secondary air vent between the gas burner and the elongate protector may flow into the oven cavity along this flow passage. The elongate protector may extend in a direction perpendicular to the base of the oven cavity. The elongate protector may extend in a direction perpendicular to the base of the oven cavity, whereby at a given vertical distance from the base of the oven cavity the elongate protector may comprise a bend, beyond which the protector is bent towards the interior of the oven cavity. The elongate burner may also extend in a direction perpendicular to the base of the oven cavity, and furthermore may at a given vertical distance from the base of the oven cavity comprise a bend. In this manner, the elongate burner may follow the internal shape of the enclosing dome. In such a way a flow passage may be formed between the elongate protector and the enclosing dome. Secondary air entering the oven cavity via the secondary air vent between the gas burner and the enclosing dome may flow into the oven cavity along this flow passage. The elongate protector may extend beyond the elongate gas burner. The elongate protector may extend beyond the elongate gas burner in such a way as to block any direct line of sight between the elongate gas burner and the baking stone or the base of the oven cavity. The bend in the elongate protector may be at a distance above the baking surface of the baking stone of between 10 mm and 40 mm. The oven may comprise a visor in an upper region of the access port. The visor may reduce heat loss through the access port. The visor may be light-permeable, e.g. transparent, to enable the contents of the oven cavity to be viewed. Typically, there is a gap between the visor and the base of the access port through which food may be introduced into and removed from the oven cavity while the visor remains in place. The visor may be removable, for example by removing a screw which holds it in place. The visor may be replaceable. According to a second aspect of the present invention there is provided a method of operating a gas-burning pizza oven according to the first aspect of the invention, comprising supplying gas to the at least one elongate gas burner, and the at least one elongate gas burner combusting the gas, whereby less heating power is generated from the combustion of gas in the rearward combustion region than the forward combustion region. This reduces the temperature difference which would otherwise occur between the forward region and the rearward region of the oven cavity. According to a third aspect of the present invention, there is provided a gas-burning pizza oven comprising an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the gas-burning pizza oven; first and second elongate gas burners, extending in a direction within the oven cavity from a back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven, each gas burner comprising one or more combustion regions; the first and second elongate gas burners being on opposite sides of a cooking space within the oven cavity. The distance between the middle of the one or more combustion regions of the first elongate gas burner and the middle of the one or more combustion regions of the second elongate gas burner, across the breadth of the oven cavity, may be greater than the perpendicular distance between a first line connecting the front ends of the one or more combustion regions of the first and second elongate gas burners and a second line connecting the back ends of the one or more combustion regions of the first and second elongate gas burners, perpendicular to the breadth. In this way the width of the oven cavity may be greater than the depth. It may be that the distance between the middle of the first elongate gas burner and the middle of the second elongate gas burner, across the breadth of the oven cavity, may be greater than the perpendicular distance between a first line connecting the front ends of the first and second elongate gas burners and a second line connecting the back ends of the first and second elongate gas burners, perpendicular to the breadth. Typically there is no gas burner having a combustion region across the back end of the oven cavity, opposite the access port. It may be that the distance between the first elongate gas burner and the second elongate gas burner increases from the from back end of the oven cavity towards the front end of the oven cavity. It may be that a buffer space is present between the first and second elongate gas burners as a unit and the front end of the oven. The buffer space may be between the end of the combustion region closest to the access port and the front end of the oven. The buffer space may be between the end of an elongate gas burner closest to the access port and the front end of the oven. A buffer space between the elongate gas burners and the front of the oven serves to promote the convection cell within the oven when the burners are burning gas. The convection cell may be further promoted by the presence of a visor in an upper region of the access port. It may be that the visor and the buffer space combine in a synergetic manner to promote the convection cell. The buffer space may be at least 2cm, optionally greater than 4cm. Typically, the buffer space may be less than 10 cm. It may be that the gas-burning pizza oven comprises individual first and second controls to independently regulate the flow of gas to the first and second elongate gas burners. The flow of gas to the first elongate gas burner may thereby be independently regulated. The flow of gas to the second elongate gas burner may thereby be independently regulated. The controls may be manual controls. According to a fourth aspect of the present invention, there is provided a pizza oven comprising an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the pizza oven; the oven cavity having a width and a depth, whereby the width is greater than the depth. The pizza oven may comprise a first heater extending down one side of the oven cavity and a second heater extending down the opposite side of the oven cavity. In this case, each of the first and the second heaters is for providing heat to the oven cavity. The first and the second heaters may each be an elongated gas burner. The space between the first and the second heaters may be wider than it is deep. It may be that the average space between the first and the second heaters may be wider than it is deep. It may be that the first and second heaters are independently controllable. The first heater has a heating region. The second heater has a heating region. It may be that the distance between the middle of the heating region of the first heater, and the middle of the heating region of the second heater, across the breadth of the oven cavity, is greater than the depth of the heating region of either of the first or second heaters, measured in a direction from the access port to the opposite back of the oven cavity. It may be that the shortest distance between the heating regions of the first and second heaters is greater than the length of the heating region of either of the first or second heaters. Typically there is no heater providing heat from the back end of the oven cavity, opposite the access port. A cooking space may be present within the oven cavity. The cooking space may be the space within which food is cooked in the oven. The cooking space may be between the first and second heaters. The cooking space may be an area, for example of the base, upon which food is cooked. The cooking space may be provided by a baking stone. The cooking space may be wider than it is deep. It may be that the average width of the cooking space is greater than the average depth of the cooking space. It may be that there is a demountable partition, which, when mounted in a pizza oven as herein disclosed, splits the oven cavity into a first cooking space and a second cooking space, the first cooking space being located at one side of the oven and the second cooking space being located at the other side of the oven. In other words, the first cooking space and the second cooking space are situated side by side in the oven. When the demountable partition is mounted in the gas-burning pizza oven, the flow of gas to the first and to the second elongate gas burners (or heaters) may thereby be independently regulated to achieve different cooking temperatures in the first cooking space and in the second cooking space. The baking stone may comprise two parts, namely a first baking stone part and a second baking stone part. The baking stone parts may be separated by a partition mounting means arranged to receive the demountable partition. The first baking stone part and the second baking stone part may be physically separate from one another. Thus it may be that each of the first baking stone part and the second baking stone part sustains a temperature independent of the other baking stone part. Typically, each baking stone part corresponds to its own cooking space. In other words, the first baking stone part is typically within the first cooking space and the second baking stone part is typically within the second cooking space. The partition mounting means may be a gap between the first and the second baking stone parts. It may be that the partition mounting means runs perpendicular to the front of the oven. The access port may be referred to as a food-receiving aperture. The food-receiving aperture has a breadth greater than its vertical height to align with the dimensions of the cooking chamber, which may be a term for the oven cavity. Typically, the breadth to vertical height ratio is in the range of 10:1 to 2:1, preferably in the range 5:2 to 5:1. This dimension ratio is similar to the dimension ratio of a pizza which has a radius greater than its vertical height. Advantageously, this allows for foodstuffs with a breadth greater than vertical height (for example a pizza) to be easily inserted into the cooking chamber but also for the shield to cover a considerable portion of the opening to the cooking chamber to reduce heat loss. Typically, the height of the food-receiving aperture is at least 5% of the height of the cooking chamber. Optionally, the height of the food-receiving aperture may be at least 10% of the height of the cooking chamber. The height of the food-receiving aperture may be at least 20% of the height of the cooking chamber. The height of the food-receiving aperture may be no more than 20% of the height of the cooking chamber. Optionally the height of the foodreceiving aperture may be no more than 30% of the height of the cooking chamber. The height of the food-receiving aperture may be no more than 50% of the height of the cooking chamber. Typically, the height of the food-receiving aperture may be no more 70% of the height of the cooking chamber. The height of the food receiving aperture may be between 10% and 50% or between 20% and 40% of the height of the cooking chamber. Typically, the height of the food-receiving aperture is at least 40% of the height from the food-receiving base to the top of the cooking chamber. Optionally, the height of the food-receiving aperture is at least 50% of the height from the food-receiving base to the top of the cooking chamber. Optionally, the height of the food-receiving aperture is at least 60% of the height from the food-receiving base to the top of the cooking chamber. Optionally, the height of the food-receiving aperture may be between 40% to 70% or 50% to 70% of the height from the food-receiving base to the top of the cooking chamber. The height of the food-receiving aperture is typically at least 2cm, at least 5cm, or least 10cm. The height of the food-receiving aperture may be less than 20cm, less than 15cm, less than 10cm or even less than 5cm. The height of the food-receiving aperture may be between 3cm and 10cm or between 5cm and 12cm or between 6cm and 10cm. Advantageously, the above size ranges provide a good balance between providing a space to enable food, particularly a pizza to be put into or removed from the oven whilst also retaining heat within the cooking chamber and in particular retaining the convection cell. It may be that the oven does not have a chimney to allow gas to exit the oven cavity upwards. There may be no chimney in the roof of the oven cavity. It may be that the open access port provides the predominant or only path for exhaust gases to leave the oven cavity. Still further, the idea of varying the total aperture area per unit length along the length of an elongate gas burner is useful for gas-burning pizza ovens with other configurations, for example, with an elongate gas burner in a back region of the oven cavity. Thus, according to a fifth aspect of the present invention there is provided a gas-burning pizza oven comprising: an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the gas-burning pizza oven; at least one elongate gas burner having one or more apertures for gas egress, whereby the total aperture area of the one or more apertures per unit length varies along the length of the at least one elongate gas burner. It may be that at least one elongate gas burner extends across at least the majority of the breadth of a back region of the oven cavity. The back region of the oven cavity may be opposite the access port. It may be that the only gas burner or burners in the pizza oven is the at least one elongate gas burner which extends across at least the majority of the breadth of a back region of the oven cavity. It may be that no elongate gas burners extend along either side of the oven cavity, from the front to the back of the oven cavity. Nevertheless, it may that at least one elongate gas burner extends in a direction within the oven cavity from a back end of the gas-burning pizza oven towards the front end of the gasburning pizza oven, whereby the at least one elongate gas burner is configured to provide less heating power to the oven cavity at a rearward combustion region of the at least one gas burner than at a frontward combustion region of the at least one gas burner. Thus the gasburning pizza oven may be a gas-burning pizza oven according to the first aspect. It may be that the total aperture area per unit length is higher at outward combustion regions of the elongate gas burner than in an intermediate combustion region, between the outward combustion regions, or the total aperture area per unit length is lower at outward combustion regions of the elongate gas burner than in an intermediate combustion region, between the outward combustion regions. It may be that the at least one gas burner comprises a plurality of apertures and the total aperture area of the apertures per unit length varies along the length of the at least one elongate gas burner. It may be that the at least one gas burner comprises three or more apertures and the total aperture area of the apertures per unit length varies along the length of the at least one elongate gas burner. It may be that the number of apertures per unit length varies along the length of the at least one elongate gas burner. It may be that the cross sectional area of apertures varies along the length of the at least one elongate gas burner. It may be that the or each of the at least one elongate gas burner comprises a single elongate slot. The mean width of the slot may vary along the length of the elongate gas burner to thereby vary the total aperture area per unit length. It may be the at least one elongate gas burner comprises a plurality of gas pipes each comprising one or more of the said apertures, optionally with gaps between the gas pipes. Thus, that at least one elongate gas burner may comprise one or more gaps between combustion regions. According to a sixth aspect of the present invention there is provided a method of operating a gas-burning pizza oven according to the fifth aspect of the invention, comprising supplying gas to the at least one elongate gas burner, and the at least one elongate gas burner combusting the gas, whereby the amount of heating power generated from the combustion of gas in the oven cavity varies along the length of the at least one elongate gas burner. Features described as optional in respect of any particular aspect of the invention are optional features of each aspect of the invention if not already explicitly described as being so, except where incompatible. Description of the Drawings An example embodiment of the present invention will now be illustrated with reference to the following Figures in which: Figure 1A is a side cross-sectional view of a gas-burning pizza oven according to an example of the present disclosure; Figure 1B is a front cross-sectional view of the same oven taken along the line A-A’; Figure 2 is a detailed schematic cross-sectional view a gas burner positioned within the oven cavity of a gas-burning pizza oven according to an example of the present disclosur; Figure 3 is a plan view of the oven cavity of a gas-burning pizza oven according to an example of the present disclosure; Figure 4 shows schematic views of different aperture arrangements in a gas burner. Figure 4(a) is an arrangement where the aperture size increases along the length of the elongate gas burner; Figure 4(b) is an arrangement in which the width of the apertures increases along the length of the elongate gas burner; Figure 4(c) is an arrangement in which the length of the apertures increases along the length of the elongate gas burner; Figure 4(d) is an arrangement in which the density of apertures increases along the length of the elongate gas burner; Figure 4€ is an arrangement in which the width of a slit aperture increases along the length of the elongate gas burner; Figure 4(f) is an arrangement in which a slit aperture has a maximum width towards the front end, but not at the front end and with a further combustion zone at the rear; Figure 4(g) is an arrangement where a number of apertures per unit length increases from a rearward combustion region to a frontward combustion region but there is also a further combustion region, behind the rearward combustion region, with a greater number of apertures per unit length than in the rearward combustion region; Figure 5 is a plan view of a further example of a gas-burning pizza oven; Figure 6 is a plan view of an alternative gas-burning oven with a gas burner across the rear wall; and Figure 7 is a plan view of a gas burner in the embodiment of Figure 6. Detailed Description of an Example Embodiment There is provided a gas-burning pizza oven 100, described with reference to Figures 1A and 1B. The pizza oven comprises an oven cavity 120 within which foodstuffs, typically pizzas, are cooked. The oven cavity is defined by a body 102. The oven comprises legs 160 on which the oven may be supported on a surface. The oven comprises a base 138, which forms the base 138 of the oven cavity 120. A baking stone 126 is positioned on the base 138. A pizza to be cooked (not illustrated) is placed on the baking stone 126. The oven comprises a ceiling 104. The ceiling forms 104 an enclosing dome 106 which contributes to the form of the oven cavity 120. The gas-burning pizza oven 100 has a front end 224 and a back end 222. An access port 110 is positioned at the front end 224 of the oven. A pizza to be cooked in the oven is inserted into the oven through the access port 110. A pizza which has been cooked in the oven is removed through the same access port 110. The oven cavity 120 comprises a forward region 124, situated towards the front end 224 of the oven, and a rearward region 122, situated towards the back end of the oven 222. A transparent visor 108 is present at the top of the access port 110 to reduce heat loss from the oven while providing a space for foodstuffs to be introduced and removed and to provide the oven operator with protection from heat from the oven 100 while enabling cooking food to be viewed. The visor is demountably attached to the body of the oven by a screw. Extending within the oven cavity 120 from the back end of the oven 222 towards the front end of the oven 224 is an elongate gas burner. The gas burner is not seen in the cross-sectional section of Figure 1A. Figure 1B shows a cross-sectional view of the oven through line A-A’. In the embodiment illustrated in Figure 1B, gas burner comprises first elongate gas burner 128a, which extends along one side of baking stone 126, and second elongate gas burner 128b, which extends along the opposite side of baking stone 126. An elongate protector 134a, 134b extends along each side of baking stone 126, between the baking stone 126 and the elongate gas burner 128a, 128b. The elongate protector 134a, 134b, serves several technical roles. The oven is designed to cook the pizza using a raised temperature in the oven cavity 120. The flames 146a, 146b produced by the elongate gas burner 128a, 128b serve to raise and maintain the temperature of the oven cavity 120. One of the roles of the elongate protector is to act as a shield against radiative heat between the flame produced by the elongate gas burner 128a, 128b and food being cooked on the baking stone 126. The elongate protector avoids singeing of the pizza by the flames 146a, 146b. The space for placing food to be cooked (the cooking space) is between the elongate protectors and generally corresponds to the shape of the baking stone. Each elongate gas burner 128a, 128b has a series of apertures 150 distributed along its length (see Figures 4a to 4e). Gas exits the burner body through these apertures 150, forming the flames 146a, 146b which heat the oven cavity 120. Each gas burner 128a, 128b is arranged so that the apertures 150 are directed towards the enclosing dome 106 in such a way that the flames 146a, 146b produced follow the internal form of the enclosing dome 106. Each elongate gas burner 128a, 128b has a combustion region extending from the aperture closest to the back of the oven to the aperture closest to the front of the oven. Each elongate gas burner 128a, 128b is configured so that the heating power provided by the flames 146a, 146b at a rearward combustion region 123 of the elongate gas burner closest to the back end of the gas-burning pizza oven 222 is different to the heating power at a forward combustion region 125 of the elongate gas, close to the front end of the gas-burning pizza oven 224. In this way, less heating power to the oven cavity is provided at the rearward combustion region of the gas burner 123 than at the forward region 125 and so the rearward region of the oven cavity 122, adjacent the rearward combustion region 123 of the gas burners, is heated less than the forward combustion region of the oven cavity 124, adjacent the forward combustion region 125 of the gas burners. The heating power in the illustrated embodiment is varied by varying the size of the apertures 150 along the length of the elongate gas burner. As a result, the temperature difference between the forward region 124 and rearward region 122 of the baking stone is reduced compared to the pronounced lower temperature at the forward region 124 than the rearward region 122 which would be the case if the heating power at the forward and rearward combustion regions 125, 123 of the gas burners was the same, given the loss of heat through the access port 110 and the greater width of baking stone at the forward region 124 than the rearward region 122. In an example, the size or number of the apertures is configured to obtain the same stone temperature at the forward region 124 and rearward region 122 at a target oven temperature (e.g. 400 C°), despite these factors. Extending along the length of each elongate gas burner is a secondary air inlet. In the embodiment illustrated in Figure 2, the secondary air inlet 136b, 137b extends along the length of the gas burner on two sides. The secondary air inlet 136b extends along the length of the gas burner 128b between the gas burner 128b and the wall formed by the enclosing dome 106. The secondary air inlet 137b also extends along the length of the gas burner 128b between the gas burner 128b and the elongate protector 134b. Air from the atmosphere surrounding the oven is sucked into the oven cavity 120 through the secondary air inlet 136b, 137b and forms a sheath layer to the gas exiting the apertures 150 of the elongate gas burner 128b. The oxygen provided by the air entering through the secondary air inlet helps to produce a clean flame. The air path produced by the sheath serves to maintain the flame shape around the inside of the enclosing dome 106. Figure 3 shows a cross-sectional plan view of the oven cavity. The elongate gas burner 128a extending along one side of the oven is connected to elongate gas burner 128b extending along the opposite side of the oven. A common gas inlet 140 supplies the elongate gas burner on both sides of the oven. An ignition device 142 ignites the gas to create the initial flame upon startup of the oven. Secondary air inlet 136a, 137a and secondary air inlet 136b and 137b are each formed from a series of inlets. Elongate protector 134a and elongate protector 134b exist between the elongate gas burner and the baking stone 126. Baking stone 126 has an isosceles trapezoidal form to match the shape of the oven cavity 120. Figure 4 illustrates five examples of elongate gas burner 128a aperture configurations. In these figures the rear of the burner is shown to the left of the figure, and the front to the right. Figure 4(a) is an arrangement where the aperture size increases along the length of the elongate gas burner. Figure 4(b) is an arrangement in which the width of the apertures increases along the length of the elongate gas burner. Figure 4(c) is an arrangement in which the length of the apertures increases along the length of the elongate gas burner. Figure 4(d) is an arrangement in which the density of apertures increases along the length of the elongate gas burner. Figure 4(e) is an arrangement in which the width of a slit aperture increases along the length of the elongate gas burner. Figure 4(f) is an arrangement in which a slit aperture has a maximum width towards the front end, but not at the front end. An expansion in the aperture width is present at the rear end of the aperture. Figure 4(g) is an arrangement where a number of apertures per unit length increases from a rearward combustion region to a frontward combustion region but there is also a further combustion region, behind the rearward combustion region, with a greater number (and therefore total area) of apertures per unit length. In each case the rearward combustion region is shown generally as 152, the frontward combustion region as 154. In the case of 4(g) and 4(h) the further combustion region, behind the rearward combustion region 152 allows some additional combustion at the back to maintain a desired temperature at the back of the oven cavity while still providing the benefit of avoiding a substantial temperature drop towards the front over the oven cavity. Figure 5 is a plan view of the interior of a gas-burning pizza oven have a cooking area with a different aspect ratio to the oven of Figure 3. Corresponding features are labelled with corresponding numbers. The baking stone is formed from two parts, 126a, 126b which extend across the breadth of a cooking area defined between elongate protectors 134a, 134b on either side of the cooking area. The overall shape of the baking stone is an isosceles trapezoid. First and second elongate gas burners 128a and 128b extend from the back of the oven 222 towards the front of the oven 224, and are angled outward such that they are further apart at their fronts than their backs. In this example secondary air inlets 136a, 136b are provided only between the elongate gas burners and the wall formed by the dome 106. Each elongate gas burner has a combustion region 127, shown with dots, and in this embodiment it is optional whether each combustion region comprises a forward combustion region which generates greater heating power than a rearward combustion region, as before, or whether heating is consistent along the length of each combustion region. There is no elongate gas burner across the back of the oven cavity 226. An access port extends across the front of the oven 224 as before, with a visor in an upper region, as per Figure 1A. The area between the combustion regions of the elongate gas burners is quadrilateral. The distance between the middle of the combustion region of the first elongate gas burner and the combustion region of the second elongate gas burner, shown by arrow 230, is greater than the distance between the front of combustion regions and the back of the combustion regions at right angles to this, shown by arrow 240. This area, between the combustion regions of the elongate gas burners, is broader (across the width of the oven cavity) than it is deep (parallel to the depth of the oven cavity). Note that the cooking space is not quite as wide as the space between the first and second elongate gas burners because it is delimited by the elongate protectors. We have found that this aspect ratio of the area delimited by the combustion regions of the elongate gas burners, which is wider than it is deep, with burners at opposite sides of the cooking space, with the access port 110 at the front, and typically without a burner across the back wall, is surprisingly advantageous for a number of reasons. Firstly, when used to cook a relatively large pizza it is advantageous for the flames to be on opposite sides of the pizza, heating opposite sides. The pizza can then be turned once, by 90°, to facilitate even cooking from all sides. This would not be the case if there was a burner across the back wall and one or both side walls. Secondly, it is possible to cook two smaller diameter pizzas at once, side by side, in which case it is possible to remove one of the pizzas at a time. Each will receive radiant heat from flames from an individual burner, whilst also being heated by the air in the oven cavity and by the baking stone. For example, the cooking space may have a breadth of at least 24 inches (61cm), to cook a 24 inch (61cm) diameter pizza, but also be usable to cook two pizzas of up to 12 inch (30.5cm) diameter, side by side. Embodiments with no burner at the back wall have the advantage that if a pizza slides when a peel is pushed under it, to remove it, the pizza is not slid towards a burner. This configuration, with a cooking surface which is wider than it is deep, works well with one or more of the features described above of: - An isosceles trapezoidal baking surface and burners which are spaced further apart at the front than the back, as this allows additional space for loading and removing pizza; burners, as described above, which generate more heat in a forward combustion region than a rearward region, which compensate for heat loss through the access port; - a visor in an upper region of the access port, which restricts heat loss through the access port while still allowing one or more pizza to be loaded and unloaded. In addition, separate gas flow controls are provided for the burners on either side, which independently control the gas supply rate to the burners. In contrast to a device with burners along the back wall and at least one side, where evenness of heating is the higher priority, the separation of the burners onto opposite sides of the cooking surface means that it is technically advantageous to provide the option of different gas flows to the gas burners on opposite sides, and so different heating powers. This enables two pizzas side by side to be cooked with different radiant heat, or for adjustments to be made to the temperature within the oven and across the baking stone as pizzas are loaded or removed at different sides of the baking chamber. However, the burners can be adjusted to have corresponding heating power when cooking a single larger pizza or if there is a desire to cook a larger pizza with more than one rotation step. In one embodiment, a slot in the baking stone 126 serves as a mounting slot 144 in which a partition 146 may be mounted. The unmounted partition is illustrated in Figure 5. The position of the slot defines the two parts 126a, 126b of the baking stone 126. The partition 146 when mounted creates a first cooking space 148a and a separate second cooking space 148b. The partition need not fully separate the first cooking space from the second cooking space. The temperature of each of the first cooking space 148a and the second cooking space 148b may be regulated independently of each other by adjusting the gas flow to the burners, or by adjusting the heating power to whatever heat supply heats the oven. Thus the oven may be used with a single larger cooking space, or two smaller cooking spaces separated by a partition. The two smaller cooking spaces may be controlled to independent temperatures. It may be that only one of the first and second cooking spaces is used for cooking by lighting a single gas burner. The variation in aperture cross-sectional area per unit length of gas burner is also useful in other configurations and Figure 6 illustrates an oven with an elongate gas burner 228 extending across the majority of the breadth of the back of a pizza oven which, again has an access port 110 at the front thereof. The gas burner 228 is fed with gas from a single central inlet 240 and the gas extends outwards to either side of the gas burner. As shown in Figure 7, there is a greater number of apertures per unit length in outward regions 227a, 227b at either end of the gas burner 228 than in an intermediate region 229 which is therebetween. This configuration is advantageous in that it allows the outside edges of the oven to be heated more than the centre which we have found gives reduced temperature variation across the width of the baking stone. Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to and do not exclude other components, integers, or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A gas-burning pizza oven comprising:an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the gas-burning pizza oven;at least one elongate gas burner having one or more apertures for gas egress, whereby the total aperture area of the one or more apertures per unit length varies along the length of the at least one elongate gas burner.

2. A gas-burning pizza oven according to claim 1 wherein the at least one elongate gas burner extends in a direction within the oven cavity from a back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven;whereby the at least one elongate gas burner is configured to provide less heating power to the oven cavity at a rearward combustion region of the at least one gas burner than at a frontward combustion region of the at least one gas burner.

3. A gas-burning pizza oven according to claim 1 wherein at least one elongate gas burner extends across at least the majority of the breadth of a back region of the oven cavity.

4. A gas-burning pizza oven according to any one preceding claim, wherein the total aperture area of apertures per unit length is higher at outward combustion regions of the elongate gas burner than in an intermediate combustion region, between the outward combustion regions.

5. A gas-burning pizza oven according to any one of claims 1 to 3, wherein the total aperture area of apertures per unit length is lower at outward combustion regions of the elongate gas burner than in an intermediate combustion region, between the outward combustion regions.

6. A gas-burning pizza oven according to any one preceding claim, wherein the number of apertures per unit length varies along the length of the at least one elongate gas burner.

7. A gas-burning pizza oven wherein the at least one elongate gas burner comprises a plurality of gas pipes each comprising one or more of the said apertures, optionally with gaps between the gas pipes.

8. A gas-burning pizza oven comprising:an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the gas-burning pizza oven;at least one elongate gas burner, extending in a direction within the oven cavity from a back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven;whereby the at least one elongate gas burner is configured to provide less heating power to the oven cavity at a rearward combustion region of the at least one gas burner than at a frontward combustion region of the at least one gas burner.

9. A gas-burning pizza oven according to claim 8, whereby said at least one elongate gas burner comprises a first elongate gas burner and a second elongate gas burner, wherein each of the first elongate gas burner and the second elongate gas burner extends in a direction within the oven cavity from a back end of the oven cavity towards a front end of the oven cavity.

10. A gas-burning pizza oven according to any one of claims 8 to 9, whereby an aperture cross-section increases from the back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven.

11. A gas-burning pizza oven according to any one of claims 8 to 10 whereby a density of apertures increases from the rearward combustion region of the at least one gas burner to the frontward combustion region of the at least one gas burner.

12. A gas-burning pizza oven according to any one of claims 8 to 11, wherein each of said at least one elongate gas burner comprises a single elongate slot, wherein the mean width of the slot is less in the rearward combustion region of the at least one gas burner than in the frontward combustion region of the at least one gas burner.

13. A gas-burning pizza oven according to any one of claims 8 to 12, wherein said at least one elongate gas burner comprises a plurality of elongate slots, whereby a slot has awidth which is increased over the width of the neighbouring slot positioned closer to the back end of the oven.

14. A gas-burning pizza oven according to any one of claims 8 to 13, comprising a gas supply path, the gas supply path arranged to supply a flow of gas fuel from a back end of the at least one elongate gas burner to a front end of the at least one elongate gas burner.

15. A gas-burning pizza oven according to any one of claims 8 to 14, whereby the oven cavity has a width which increases from the back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven and wherein there are first and second elongate gas burners and wherein the distance between them increases from the back end of the oven cavity towards the front end of the oven cavity.

16. A gas-burning pizza oven according to any one of claims 8 to 15, whereby the oven cavity has a cooking space which is trapezoidal and a baking stone which is trapezoidal.

17. A gas-burning pizza oven according to any one of claims 8 to 17, whereby each of said at least one elongate gas burner comprises one or more apertures distributed along its length.

18. A gas-burning pizza oven according to any one of claims 8 to 17, comprising for said at least one elongate gas burner an elongate protector which extends along the length of said at least one elongate gas burner, between said at least one elongate gas burner and the cooking space.

19. A gas-burning pizza oven according to any one of claims 8 to 18, comprising an air vent which extends along the length of each of said at least one elongate gas burner between said at least one elongate gas burner and the wall of the oven cavity proximate said at least one elongate gas burner.

20. A gas-burning pizza oven according to any one of claims 8 to 19, wherein the frontward combustion region of the at least one gas burner is positioned closer to the access port than the rearward combustion region of the at least one gas burner is, and wherein the position of the frontward combustion region of the at least one gas burner correspondsto the position of a maximum in the heating power of the gas burner and the position of the rearward combustion region of the at least one gas burner corresponds to the position of a minimum in the heating power of the gas burner.

21. A gas-burning pizza oven according to any one of claims 8 to 20, comprising a further combustion region of the at least one gas burner, rearward of the rearward combustion region, which is configured to provide more heating power to the oven cavity than at the rearward combustion region.

22. A method of operating a gas-burning pizza oven according to any one of claims 8 to 21, the method comprising supplying gas to the at least one gas burner, and the gas burner combusting the gas, whereby less heating power is generated from the combustion of gas in the rearward region than the forward region.

23. A gas-burning pizza oven comprising an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the gas-burning pizza oven;first and second elongate gas burners, extending in a direction within the oven cavity from a back end of the gas-burning pizza oven towards the front end of the gas-burning pizza oven, each gas burner comprising one or more combustion regions;the first and second elongate gas burners being on opposite sides of a cooking space within the oven cavity.

24. A gas-burning pizza oven according to claim 23, wherein the distance between the middle of the one or more combustion regions of the first elongate gas burner and the middle of the one or more combustion regions of the second elongate gas burner, across the breadth of the oven cavity, is greater than the perpendicular distance between a first line connecting the front ends of the one or more combustion regions of the first and second elongate gas burners and a second line connecting the back ends of the one or more combustion regions of the first and second elongate gas burners, perpendicular to the breadth.

25. A gas-burning pizza oven according to either claim 23 or claim 24, wherein there is no gas burner having a combustion region across the back end of the oven cavity, opposite the access port.

26. A gas-burning pizza oven according to any one of claims 23 to 25, comprising individual first and second controls to independently regulate the flow of gas to the first and second elongate gas burners.

27. A gas-burning pizza oven according to any preceding claims, comprising a visor in an upper region of the access port.

28. A pizza oven comprising an oven cavity with an access port to receive food into the oven cavity for cooking, and to remove cooked food, the access port being at a front end of the pizza oven;the oven cavity having a width and a depth, whereby the width is greater than the depth; anda first heater extending down one side of the oven cavity and a second heater extending down the opposite side of the oven cavity.

29. A pizza oven according to claim 28, wherein the first and second heaters are independently controllable.

30. A pizza oven according to claim 28 or claim 29, additionally comprising a demountable partition which splits the oven cavity into a first cooking space and a second cooking space.

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