Fuel system of a jet engine

A fuel system comprises a fuel pump (10) operable to deliver fuel through a supply line (14) to a pressure raising valve (18), the pressure raising valve (18) including a control chamber (32), the fuel pressure within the control chamber (32) controlling a minimum pump pressure differential, and an actuator control servo-valve (60) operable to control the supply of fuel from the supply line (14) to an actuator control line (56, 58), wherein the actuator control servo-valve (60) further controls the pressure of fuel applied to the control chamber (32) of the pressure raising valve (18).