The Tortoise Heavy Assault Tank was a British heavy assault gun design developed during the Second World War, but never put into mass production. It was developed for the task of clearing heavily fortified areas such as the Siegfried Line and as a result favoured armour protection over mobility.
Six prototypes were constructed, but it never went into production. Five prototypes were scrapped and one was preserved, and can now be found at The Tank Museum.
Although heavy, at 78 tons, and not readily transported, it was considered reliable and a good gun platform.
Battlefront are going to produce a 15mm version for their Late War Leviathans game.