Abstract: The present invention is particularly concerned with the supply of fuel to fuel servos of gas turbine engines. A check valve (62) is positioned in a return pipe (40, 24, 22, 26) from a fuel spill valve (12) to the upstream low pressure side of a high pressure pump (10). An aperture (32) in a piston (30) of the check valve (62) produces a predetermined pressure drop across the check valve (62) when the flow of excess fuel reaches a predetermined value. A fuel servo shut off valve (64) is positioned in a pipe (42, 58) connecting a fuel flow regulator (14) to a fuel servo (80). A piston (46) of the fuel servo shut off valve (64) initially closes a chamber (56) to prevent fuel being supplied to the fuel servo (80), from the fuel flow regulator (14). The piston (46) of the fuel servo shut off valve (64) is moved against a spring (48) when the predetermined pressure drop is formed across the check valve (62) to allow fuel to be supplied from the fuel flow regulator (14) to the fuel servo (80) via chamber (56).