A ballscrew actuator comprising: a ballnut having at least one first helical groove formed on a radially inner surface and defining an axis; a ballscrew disposed along the axis within the ballnut, the ballscrew having at least one second helical groove formed on a radially outer surface and opposed to the first helical groove so as to form at least one helical raceway; a plurality of balls or rolling elements disposed in the at least one helical raceway; the ballscrew being movable relative to the ballnut between a stowed position and a deployed position; characterised in that the ballscrew comprises: a ballscrew bore extending axially therein; a lubrication piston mounted for sliding movement within the ballscrew bore and dividing the ballscrew bore axially into a lubricant receiving portion and a pressurising portion; and at least one lubrication passage extending between the lubricant receiving portion of the ballscrew bore and an interface between the ballscrew and the ballnut; the actuator further comprising: a pump; wherein the pump comprises: a pump chamber having an outlet in fluid communication with the pressurising portion of the ballscrew bore; an air inlet passage for admitting air into the pump chamber; and a pumping piston movable in a pumping direction for pressurising air in the pump chamber, the pumping piston being configured and arranged such that it is moved in the pumping direction as the ballscrew moves axially relative to the ballnut by engagement with an opposing structure of the actuator during movement of the ballscrew between its stowed and deployed positions; the pressurised air moving into the pressurising portion of the ballscrew bore through the outlet so as to move the lubrication piston therein, thereby to move lubricant through the lubrication passage. a ballnut having at least one first helical groove formed on a radially inner surface and defining an axis; a ballscrew disposed along the axis within the ballnut, the ballscrew having at least one second helical groove formed on a radially outer surface and opposed to the first helical groove so as to form at least one helical raceway; a plurality of balls or rolling elements disposed in the at least one helical raceway; the ballscrew being movable relative to the ballnut between a stowed position and a deployed position; characterised in that the ballscrew comprises: a ballscrew bore extending axially therein; a lubrication piston mounted for sliding movement within the ballscrew bore and dividing the ballscrew bore axially into a lubricant receiving portion and a pressurising portion; and at least one lubrication passage extending between the lubricant receiving portion of the ballscrew bore and an interface between the ballscrew and the ballnut; a ballscrew bore extending axially therein; a lubrication piston mounted for sliding movement within the ballscrew bore and dividing the ballscrew bore axially into a lubricant receiving portion and a pressurising portion; and at least one lubrication passage extending between the lubricant receiving portion of the ballscrew bore and an interface between the ballscrew and the ballnut; the actuator further comprising: a pump; wherein the pump comprises: a pump chamber having an outlet in fluid communication with the pressurising portion of the ballscrew bore; an air inlet passage for admitting air into the pump chamber; and a pumping piston movable in a pumping direction for pressurising air in the pump chamber, the pumping piston being configured and arranged such that it is moved in the pumping direction as the ballscrew moves axially relative to the ballnut by engagement with an opposing structure of the actuator during movement of the ballscrew between its stowed and deployed positions; the pressurised air moving into the pressurising portion of the ballscrew bore through the outlet so as to move the lubrication piston therein, thereby to move lubricant through the lubrication passage. a pump; wherein the pump comprises: a pump chamber having an outlet in fluid communication with the pressurising portion of the ballscrew bore; an air inlet passage for admitting air into the pump chamber; and a pumping piston movable in a pumping direction for pressurising air in the pump chamber, the pumping piston being configured and arranged such that it is moved in the pumping direction as the ballscrew moves axially relative to the ballnut by engagement with an opposing structure of the actuator during movement of the ballscrew between its stowed and deployed positions; a pump chamber having an outlet in fluid communication with the pressurising portion of the ballscrew bore; an air inlet passage for admitting air into the pump chamber; and a pumping piston movable in a pumping direction for pressurising air in the pump chamber, the pumping piston being configured and arranged such that it is moved in the pumping direction as the ballscrew moves axially relative to the ballnut by engagement with an opposing structure of the actuator during movement of the ballscrew between its stowed and deployed positions; the pressurised air moving into the pressurising portion of the ballscrew bore through the outlet so as to move the lubrication piston therein, thereby to move lubricant through the lubrication passage.