A roll control system comprising a front torsion bar; a front first hydraulic actuator attached to the front torsion bar; a rear torsion bar; a rear first hydraulic actuator attached to the rear torsion bar; and control means connected to the hydraulic actuators and controlling the operation thereof on detection of a predetermined vehicle condition; wherein each hydraulic actuator comprises a first fluid chamber and a second fluid chamber; wherein the control means comprises a source of fluid pressure, a fluid reservoir, a pressure control valve fluidly connected between the pressure source and the reservoir, two pressure relief valves each having two positions to selectively fluidly connect the fluid chambers of the hydraulic actuators either to the pressure source or to the fluid reservoir, and a directional valve fluidly connected between the pressure relief valves and the fluid chambers of the hydraulic actuators; wherein the pressure relief valves and the directional valve are positioned on detection of the predetermined vehicle condition to apply a fluid pressure to the first fluid chamber of the first front and rear hydraulic actuators, and/or to apply a fluid pressure to the second fluid chamber of the first front and rear hydraulic actuators.