A valve assembly is provided, the valve assembly comprising a valve housing; an inlet for fluid entering the valve housing; an outlet for fluid leaving the valve housing; a flow control assembly disposed within the valve housing between the inlet and the outlet, whereby fluid entering the valve housing is caused to flow through the flow control assembly, the flow control assembly comprising a cage having apertures therethrough to provide passage for fluid passing from the inlet to the outlet; a closure assembly having a first closure member disposed within the cage and moveable with respect to the cage between a first closed position, in which the first closure member closes the innermost end of all of the apertures in the cage, and a second open position, in which the innermost end of all the apertures in the cage are open; and a second closure member disposed outside the cage and moveable with respect to the cage between a first closed position, in which the second closure member closes the outermost end of all of the apertures in the cage, and a second open position, in which the outermost end of all the apertures in the cage are open.