Anti-theft steering lock

A system for steering the wheels (40) of a vehicle V. The system includes a steering gear (36) provided with a steering rack (42) reciprocable in a power cylinder (44), A steering shaft (12) has a pinion (34) meshing with the steering rack (42). A hydraulic fluid system (60) assists the reciprocation of the steering rack (42). The hydraulic fluid system (60) includes a power piston (70) reciprocable in the power cylinder (44). A control valve (62) directs hydraulic fluid from a pump (64) to the power cylinder (44) at one side or the other of the piston (70), depending on the direction of rotation of the steering shaft (12). A lock valve (86, 92) is operable when closed to lock the rack (42) against reciprocation to prevent steering of the wheels (40) by preventing fluid flow in the hydraulic fluid system (60). The lock valve (86, 92) is controlled by a solenoid-operated electronic controller (90).