Erroneously referred to as the FV215B (a hybrid of the Conqueror and FV 215 which never existed even in blueprints), the FV215 was the sister tank to the FV214 Conqueror. The 215 was the reason that the FV4005 was constructed, that being a test bed for the new 183mm gun that was meant to be the main armament of Britain’s forefront heavy tank. The conqueror would be armed with a 120mm gun, as a more conventional heavy tank, while the FV215 would’ve been a heavy gun tank designed to knock out heavy Soviet armor like the IS-3 in a single devastating blow, without the risk of a ricochet. The 183mm gun proved to be comedically impractical, and the FV215 was ultimately never completed.