An invaginating device including: an inner elongate member; an outer flexible tube with invaginated axial ends, which outer flexible tube defines a radial inner surface and a radial outer surface, and is: disposed at or near a first axial end of the inner elongate member; concentric with the inner elongate member; extendable to protrude from the first axial end of the inner elongate member and retractable to reduce such protrusion from the first axial end of the inner elongate member; fluid within the radial gap defined between the inner elongate member and the outer flexible tube, which fluid is either: (i) pressurized; or (ii) a non-compressible fluid; and an actuator that is: movable relative to the inner elongate member; and engageable with the outer flexible tube to extend the outer flexible tube relative to the first axial end of the inner elongate member; characterised in that: the outer flexible tube is sized to provide a radial gap between the inner elongate member and the outer flexible tube; and the radial inner surface of the outer flexible tube is sealably connected at the axial ends of the outer flexible tube to the radial outer surface of the inner elongate member, with the axial spacing between such sealed axial ends being less than the axial length of the outer tube. an inner elongate member; an outer flexible tube with invaginated axial ends, which outer flexible tube defines a radial inner surface and a radial outer surface, and is: disposed at or near a first axial end of the inner elongate member; concentric with the inner elongate member; extendable to protrude from the first axial end of the inner elongate member and retractable to reduce such protrusion from the first axial end of the inner elongate member; disposed at or near a first axial end of the inner elongate member; concentric with the inner elongate member; extendable to protrude from the first axial end of the inner elongate member and retractable to reduce such protrusion from the first axial end of the inner elongate member; fluid within the radial gap defined between the inner elongate member and the outer flexible tube, which fluid is either: (i) pressurized; or (ii) a non-compressible fluid; and an actuator that is: movable relative to the inner elongate member; and engageable with the outer flexible tube to extend the outer flexible tube relative to the first axial end of the inner elongate member; characterised in that: the outer flexible tube is sized to provide a radial gap between the inner elongate member and the outer flexible tube; and the radial inner surface of the outer flexible tube is sealably connected at the axial ends of the outer flexible tube to the radial outer surface of the inner elongate member, with the axial spacing between such sealed axial ends being less than the axial length of the outer tube. movable relative to the inner elongate member; and engageable with the outer flexible tube to extend the outer flexible tube relative to the first axial end of the inner elongate member; the outer flexible tube is sized to provide a radial gap between the inner elongate member and the outer flexible tube; and the radial inner surface of the outer flexible tube is sealably connected at the axial ends of the outer flexible tube to the radial outer surface of the inner elongate member, with the axial spacing between such sealed axial ends being less than the axial length of the outer tube.