<p>A seal assembly (30) and a running tool (20) are provided for sealing a casing annulus in a wellhead (14). A casing hanger (12) includes a radially external groove therein, and wellhead has a radially internal groove therein. A locking ring (36) may be actuated by the running tool to move into the internal recess in the wellhead and thereby axially connect the seal assembly and the wellhead. Another locking ring (40) is radially movable to connect the seal assembly to the casing hanger. The seal assembly seals the casing annulus while being interconnected with the wellhead and the casing hanger.</p>
