FV4005

The FV4005 has what is almost certainly the largest gun ever fitted to a tank. It marks the high point of the race throughout the history of armoured warfare to build bigger and bigger guns that could defeat thicker and thicker armour at longer and longer range. After this point, the advent of guided missiles and more advanced gun ammunition would allow this improvement to continue, but at far lower size and weight.

The vehicle itself originated in the late 1940s. The British Army realised they needed to reliably destroy new Soviet heavy tanks such as the IS-3 and its potential successors well beyond the range that they could return fire, but they had no gun that could hope to do this. They began a project to develop one.

The intention was to mount the resulting weapon on a new, purpose designed vehicle, the Heavy Gun Tank Number 2, or FV215 (some sources call it Heavy Anti Tank Gun SP No.2). There were concerns that the nascent Cold War could turn hot before it was ready in numbers, so a stop gap solution was also to be developed using the in-production Centurion tank hull. This was named Heavy Gun Tank Number 1, or FV4005.