Clutch control system

A clutch control system for a motor vehicle having an engine (10) a gearbox (12) having a plurality of gear ratios, and a clutch (14) providing a drive connection between the engine and the gearbox the control system comprising a clutch actuation means (22) for controlling the state of engagement of the clutch, a control unit (36) which receives signals from a plurality of vehicle operating parameter sensors including a gear sensor (32) which indicates that a gear ratio is engaged in the gearbox, the control unit processing these signals to produce a command signal (Vc) for operation of the clutch actuating means, and an electrical power supply circuit (50,53,54) for the control unit (36), the control system being characterised in that, if on activation of the electrical power supply circuit (50,53,54) to power-up the control unit (36) the control unit receives a signal from the gear position sensor (32) indicating that a gear ratio is engaged in the gearbox, the control unit (36) inhibits disengagement of the clutch (14) by the clutch actuation means (22).