The Tortoise was developed by Nuffield Mechanization & Aero.
Design work first started in 1942. With the Germans introducing the King Tiger development was rushed, but the six prototypes weren't ready until 1946 and 1947.
Had a cast one piece superstructure.
A junior minister at the Ministry of Supply, Duncan Sandy, pushed forward the development of a heavy tank capable of carrying a 94 mm gun. It was going to be able to use a discarding sabot ammunition, which could penetrate any tank of the time.
Two of the Besa machine guns were in a cupola for anti-aircraft defense.