A valve assembly comprising: a fluid flow passage to permit a flow of a fluid through the valve assembly; a valve seat ; and an actuator assembly comprising: an actuator body in a fixed position relative to the valve seat ; a valve member moveable relative to the valve seat between a first position (P1) in which the valve member is at least partially engaged with the valve seat to at least partially block the fluid flow passage , and a second position (P2) in which the valve member is remote from the valve seat , wherein the valve member is moveable relative to the actuator body and extends around the actuator body such that the actuator body is disposed within the valve member , and a bellows received within the valve member , and attached to the valve member and to the actuator body , the bellows comprising an interior surface and an exterior surface opposite to the interior surface ; wherein the interior surface of the bellows , the actuator body , and the valve member define a control chamber therebetween, wherein the exterior surface of the bellows and the valve member define an outer volume therebetween such that the outer volume is around the control chamber , characterised in that the valve member comprises at least one orifice extending therethrough and in that the at least one orifice fluidly communicates the control chamber with the outer volume . a fluid flow passage to permit a flow of a fluid through the valve assembly; a valve seat ; and an actuator assembly comprising: an actuator body in a fixed position relative to the valve seat ; a valve member moveable relative to the valve seat between a first position (P1) in which the valve member is at least partially engaged with the valve seat to at least partially block the fluid flow passage , and a second position (P2) in which the valve member is remote from the valve seat , wherein the valve member is moveable relative to the actuator body and extends around the actuator body such that the actuator body is disposed within the valve member , and a bellows received within the valve member , and attached to the valve member and to the actuator body , the bellows comprising an interior surface and an exterior surface opposite to the interior surface ; wherein the interior surface of the bellows , the actuator body , and the valve member define a control chamber therebetween, wherein the exterior surface of the bellows and the valve member define an outer volume therebetween such that the outer volume is around the control chamber , characterised in that the valve member comprises at least one orifice extending therethrough and in that the at least one orifice fluidly communicates the control chamber with the outer volume . an actuator body in a fixed position relative to the valve seat ; a valve member moveable relative to the valve seat between a first position (P1) in which the valve member is at least partially engaged with the valve seat to at least partially block the fluid flow passage , and a second position (P2) in which the valve member is remote from the valve seat , wherein the valve member is moveable relative to the actuator body and extends around the actuator body such that the actuator body is disposed within the valve member , and a bellows received within the valve member , and attached to the valve member and to the actuator body , the bellows comprising an interior surface and an exterior surface opposite to the interior surface ; wherein the interior surface of the bellows , the actuator body , and the valve member define a control chamber therebetween, wherein the exterior surface of the bellows and the valve member define an outer volume therebetween such that the outer volume is around the control chamber , characterised in that the valve member comprises at least one orifice extending therethrough and in that the at least one orifice fluidly communicates the control chamber with the outer volume . <EOS>