An interstage seal is provided for installation between forward and aft stage discs of a turbine section of a gas turbine engine. The seal has a forward annular portion, which extends forward to contribute to an air seal at the outer periphery of the forward stage disc, and an aft annular portion, which extends rearward to contribute to an air seal at the outer periphery of the aft stage disc. The seal has a peripheral slot into which static vane inner rails are loadable. The seal includes a first component, which provides the forward annular portion, and a second component, which provides the aft annular portion. The second component is separably connectable to the first component such that the first and second components, when connected, cooperate to form the peripheral slot. Loading the static vane inner rails into the slot prevents the second component separating from the first component.