A pressure regulating shut-off valve comprising: a valve member arranged to regulate flow of a fluid between an inlet and an outlet of the pressure regulating shut-off valve; a pneumatic actuator comprising: a piston arranged for reciprocal motion in a cylinder wherein the cylinder and a first face of the piston define a first volume that is fluidly connected to the inlet of the pressure regulating shut-off valve; wherein the cylinder and a second face of the piston define a second volume that is fluidly connected via a fluid path to the inlet of the pressure regulating shut-off valve; and wherein the second face of the piston has a surface area that is greater than a surface area of the first face of the piston; wherein the pneumatic actuator further comprises: an electrically actuated valve arranged to control the flow of fluid through the fluid path; wherein the electrically actuated valve is arranged to restrict or substantially close the fluid path between the inlet of the pressure regulating shut-off valve and the second volume, when power is supplied to the electrically actuated valve; wherein the electrically actuated valve is arranged to derestrict or substantially open the fluid path between the inlet of the pressure regulating shut-off valve and the second volume, when power is removed from the electrically actuated valve; and wherein the pneumatic actuator is arranged to act on the valve member, when power is removed from the electrically actuated valve, to hold the valve member in a fixed position; characterised in that the pneumatic actuator is arranged to not interfere with the valve member, when power is supplied to the electrically actuated valve. a valve member arranged to regulate flow of a fluid between an inlet and an outlet of the pressure regulating shut-off valve; a pneumatic actuator comprising: a piston arranged for reciprocal motion in a cylinder wherein the cylinder and a first face of the piston define a first volume that is fluidly connected to the inlet of the pressure regulating shut-off valve; wherein the cylinder and a second face of the piston define a second volume that is fluidly connected via a fluid path to the inlet of the pressure regulating shut-off valve; and wherein the second face of the piston has a surface area that is greater than a surface area of the first face of the piston; wherein the cylinder and a first face of the piston define a first volume that is fluidly connected to the inlet of the pressure regulating shut-off valve; wherein the cylinder and a second face of the piston define a second volume that is fluidly connected via a fluid path to the inlet of the pressure regulating shut-off valve; and wherein the second face of the piston has a surface area that is greater than a surface area of the first face of the piston; wherein the pneumatic actuator further comprises: an electrically actuated valve arranged to control the flow of fluid through the fluid path; wherein the electrically actuated valve is arranged to restrict or substantially close the fluid path between the inlet of the pressure regulating shut-off valve and the second volume, when power is supplied to the electrically actuated valve; wherein the electrically actuated valve is arranged to derestrict or substantially open the fluid path between the inlet of the pressure regulating shut-off valve and the second volume, when power is removed from the electrically actuated valve; and wherein the pneumatic actuator is arranged to act on the valve member, when power is removed from the electrically actuated valve, to hold the valve member in a fixed position; characterised in that the pneumatic actuator is arranged to not interfere with the valve member, when power is supplied to the electrically actuated valve. wherein the electrically actuated valve is arranged to restrict or substantially close the fluid path between the inlet of the pressure regulating shut-off valve and the second volume, when power is supplied to the electrically actuated valve; wherein the electrically actuated valve is arranged to derestrict or substantially open the fluid path between the inlet of the pressure regulating shut-off valve and the second volume, when power is removed from the electrically actuated valve; and wherein the pneumatic actuator is arranged to act on the valve member, when power is removed from the electrically actuated valve, to hold the valve member in a fixed position; characterised in that the pneumatic actuator is arranged to not interfere with the valve member, when power is supplied to the electrically actuated valve.