A surgical instrument, comprising: an elongated shaft module including: an elongated shaft member; and an end effector including a pair of jaw members (140, 142) supported at a distal end of the elongated shaft member, at least one of the jaw members moveable relative to the other jaw member between open and closed positions; and a handle module including: a housing including an opening dimensioned to permit passage of the pair of jaw members (140, 142) in the closed position; and a movable handle movable relative to the housing, the movable handle operatively coupled to the pair of jaw members (140, 142) such that at least one of the jaw members is induced to move relative to the other jaw member between open and closed positions in response to movement of the movable handle with respect to the housing; and characterised by the opening extending longitudinally through the handle module and a lock movable between a first position wherein the lock engages the elongated shaft module to secure the elongated shaft module in place within the housing, and a second position wherein the lock is disengaged from the elongated shaft module to permit the elongated shaft module to be separated from the handle module. an elongated shaft module including: an elongated shaft member; and an end effector including a pair of jaw members (140, 142) supported at a distal end of the elongated shaft member, at least one of the jaw members moveable relative to the other jaw member between open and closed positions; and an elongated shaft member; and an end effector including a pair of jaw members (140, 142) supported at a distal end of the elongated shaft member, at least one of the jaw members moveable relative to the other jaw member between open and closed positions; and a handle module including: a housing including an opening dimensioned to permit passage of the pair of jaw members (140, 142) in the closed position; and a movable handle movable relative to the housing, the movable handle operatively coupled to the pair of jaw members (140, 142) such that at least one of the jaw members is induced to move relative to the other jaw member between open and closed positions in response to movement of the movable handle with respect to the housing; and characterised by the opening extending longitudinally through the handle module and a lock movable between a first position wherein the lock engages the elongated shaft module to secure the elongated shaft module in place within the housing, and a second position wherein the lock is disengaged from the elongated shaft module to permit the elongated shaft module to be separated from the handle module. a housing including an opening dimensioned to permit passage of the pair of jaw members (140, 142) in the closed position; and a movable handle movable relative to the housing, the movable handle operatively coupled to the pair of jaw members (140, 142) such that at least one of the jaw members is induced to move relative to the other jaw member between open and closed positions in response to movement of the movable handle with respect to the housing; and characterised by the opening extending longitudinally through the handle module and a lock movable between a first position wherein the lock engages the elongated shaft module to secure the elongated shaft module in place within the housing, and a second position wherein the lock is disengaged from the elongated shaft module to permit the elongated shaft module to be separated from the handle module.