A valve assembly for a power steering system conveying an input between a torsion bar and a steering gear comprising: a valve sleeve defining a cavity; a shaft extending through said cavity and being rotatable relative to said valve sleeve about an axis in a first rotational direction and a second rotational direction for conveying rotational movement from the torsion bar to the steering gear and the torsion bar for attachment to said shaft to provide rotational resistance on said shaft; a first hydraulic circuit interchangeable from an unassisted condition to an assisted condition in response to said shaft being rotated in either said first or second rotational directions a circumferential actuating distance to hydraulically actuate the steering gear; an actuator including a second hydraulic circuit interchangeable from an unengaged condition to an engaged condition to apply a circumferential hydraulic force on said shaft to overcome a rotational resistance of the torsion bar and effectuate rotation of said shaft said circumferential actuating distance in either of said first or said second rotational directions for initiating said assisted condition of said first hydraulic circuit characterised by said second hydraulic circuit including a hydraulic chamber; and said actuator including a pin dividing said hydraulic chamber into a first sub-chamber and a second sub-chamber; wherein a hydraulic pressure applied in said first sub-chamber overcomes said rotational resistance and urges said pin into said second sub-chamber to rotate said shaft relative to said valve sleeve in said first rotational direction by said circumferential actuating distance to place the first hydraulic circuit in said assisted condition; and wherein a hydraulic pressure applied in said second sub-chamber overcomes said rotational resistance and urges said pin into said first sub-chamber to rotate said shaft relative to said valve sleeve in said second rotational direction by said circumferential actuating distance to place the first hydraulic circuit in said assisted condition. a valve sleeve defining a cavity; a shaft extending through said cavity and being rotatable relative to said valve sleeve about an axis in a first rotational direction and a second rotational direction for conveying rotational movement from the torsion bar to the steering gear and the torsion bar for attachment to said shaft to provide rotational resistance on said shaft; a first hydraulic circuit interchangeable from an unassisted condition to an assisted condition in response to said shaft being rotated in either said first or second rotational directions a circumferential actuating distance to hydraulically actuate the steering gear; an actuator including a second hydraulic circuit interchangeable from an unengaged condition to an engaged condition to apply a circumferential hydraulic force on said shaft to overcome a rotational resistance of the torsion bar and effectuate rotation of said shaft said circumferential actuating distance in either of said first or said second rotational directions for initiating said assisted condition of said first hydraulic circuit characterised by said second hydraulic circuit including a hydraulic chamber; and said actuator including a pin dividing said hydraulic chamber into a first sub-chamber and a second sub-chamber; wherein a hydraulic pressure applied in said first sub-chamber overcomes said rotational resistance and urges said pin into said second sub-chamber to rotate said shaft relative to said valve sleeve in said first rotational direction by said circumferential actuating distance to place the first hydraulic circuit in said assisted condition; and wherein a hydraulic pressure applied in said second sub-chamber overcomes said rotational resistance and urges said pin into said first sub-chamber to rotate said shaft relative to said valve sleeve in said second rotational direction by said circumferential actuating distance to place the first hydraulic circuit in said assisted condition.