A moveable member is provided which extends the top surface of a substrate table, in plan, beyond a bumper which protects the substrate table during collision. The moveable member may be retracted to a retracted position in which it no longer extends beyond the bumper. In this way it is possible to move two substrate tables together and to allow the retractable member to pass under a liquid supply system which normally provides liquid between the projection system and a substrate without turning off of the liquid supply system.