A gas fire system comprises a gas valve (104), a spark generator (108) for igniting a gas flowing out of the gas valve (104), a microprocessor-based controller 106 for controlling the operation of the gas valve (104) and the spark generator (108) and a user interface (110, 112) for providing instructions to the controller (106). The gas valve (104) comprises a valve body (202) having a gas inlet (266), a main gas outlet (268) and a bore (212). The bore (212) has an interior surface (298) a part of which defines a gas flow cavity, the gas inlet (266) and the main gas outlet (268) being in communication with the gas flow cavity. The gas valve (104) further comprises a valve spindle (206) arranged to move into and out of the gas flow cavity, an exterior portion of the valve spindle forming a flow control surface (262) and defining a gap having a volume between the flow control surface (262) and the interior surface (298) of the gas flow cavity. Relative movement of the flow control surface (262) and the gas flow cavity varies the volume of the gap and regulates a flow of gas from the gas inlet (266) to the main gas outlet (268).