A hydraulic/mechanical braking system for a vehicle comprises a cam (128) keyed onto a transmission shaft or a trailing wheel and at least two hydraulic cylinder assemblies (126, 129) including a cam follower (127). A hydraulic circuit (C) connects the hydraulic cylinder assemblies together. A master brake valve (113) controls the flow of fluid in the circuit. Actuation of the master brake valve (113) obstructs the flow of fluid and hence the reciprocation of the hydraulic cylinder assemblies, forcing the cam following against the cam to resist rotation. The cam (128) is formed with two opposing flat faces (142, 143) in order to provide an anti-lock braking system (ABS).