Fuel system

A fuel system of a staged combustion engine comprising primary and secondary burners (22, 24), the fuel system comprising; a metering valve arrangement (14) for regulating fuel flow from a pump to the engine, a pressure raising shut off valve arrangement (16) for controlling the supply of metered fuel to primary and secondary delivery lines (18, 20) for communication with the primary and secondary burners (22, 24) respectively, wherein the pressure raising shut off valve arrangement is operable between an open position in which fuel flow is permitted to both the primary and the secondary burners, and a closed position in which fuel flow through the pressure raising valve arrangement to the primary and secondary burners is prevented, and, a start valve means (113) provided with by-pass flow means (115, 121) which is operable to permit an initial by-pass flow of fuel to the primary burners (22) upon engine start-up when the pressure raising shut of valve arrangement (16) is in the closed position.