A delivery system for controlled deployment of an expandable prosthesis, the delivery system comprising: an inner retention assembly comprising an inner elongate member having a proximal end and a distal end configured to carry the expandable prosthesis to an in situ target location an outer elongate hollow member having a proximal end and a distal end that is slidable over the inner retention assembly, the outer elongate hollow member configured to cover the first and second ends of the expandable prosthesis when the expandable prosthesis is mounted over the inner elongate member; and wherein the outer elongate hollow member is moveable in a distal direction relative to the inner retention assembly to uncover at least the second end of the expandable prosthesis when the expandable prosthesis is mounted over the inner elongate member, wherein distal movement of the outer elongate hollow member relative to the inner retention assembly causes longitudinal collapse of at least a portion of the outer elongate hollow member, characterized in that the inner retention assembly is configured to radially restrain a first end of the expandable prosthesis when the expandable prosthesis is mounted over the inner elongate member with the second end of the expandable prosthesis positioned proximally of the first end, wherein the delivery system further comprises a receiving member provided at the distal end of the outer elongate hollow member, wherein the distal end of the outer elongate hollow member is positioned within the receiving member and the proximal end of the outer elongate hollow member is spaced proximally away from the receiving member and a squash plate configured to cause longitudinal collapse of the outer member into the receiving member. an inner retention assembly comprising an inner elongate member having a proximal end and a distal end configured to carry the expandable prosthesis to an in situ target location an outer elongate hollow member having a proximal end and a distal end that is slidable over the inner retention assembly, the outer elongate hollow member configured to cover the first and second ends of the expandable prosthesis when the expandable prosthesis is mounted over the inner elongate member; and wherein the outer elongate hollow member is moveable in a distal direction relative to the inner retention assembly to uncover at least the second end of the expandable prosthesis when the expandable prosthesis is mounted over the inner elongate member, wherein distal movement of the outer elongate hollow member relative to the inner retention assembly causes longitudinal collapse of at least a portion of the outer elongate hollow member, characterized in that the inner retention assembly is configured to radially restrain a first end of the expandable prosthesis when the expandable prosthesis is mounted over the inner elongate member with the second end of the expandable prosthesis positioned proximally of the first end, wherein the delivery system further comprises a receiving member provided at the distal end of the outer elongate hollow member, wherein the distal end of the outer elongate hollow member is positioned within the receiving member and the proximal end of the outer elongate hollow member is spaced proximally away from the receiving member and a squash plate configured to cause longitudinal collapse of the outer member into the receiving member.