A project for a heavy coastal defense tank developed in the U.K. in the late 1950s as part of a program of coastal defense against suspected maritime landings. Impressive firepower, excellent armoring including strong sloped hull armor, and decent mobility made the vehicle a formidable opponent in combat against landing vessels. The gun was equipped with a mechanism comprising movable covers on the muzzle breaks to protect the bore from moisture.

During the tank's development it became clear that anti-ship missiles would be the future of maritime battles and not artillery guns. As a result, the project was deemed to have no prospects and was discontinued before a prototype was built.