A valve comprising a housing defining a fluid inlet, a fluid outlet and a fluid path, a valve chamber in the fluid path and having a valve seat, a valve member moveable between an open position in which the valve member is displaced from the valve seat such that the fluid inlet is connected to the fluid outlet and a closed position, and first and second opposed biasing members of unequal loading applying a resulting biasing force to the valve member so as to bias it towards the closed position, a first piston member movable in a first bore relative to the valve for moving the valve member in a first direction, and a second piston member for moving the valve member in a second direction, a first pressure compensation passage, and a second pressure compensation passage.