Well, that one super-heavy tank the Brits got to a prototype stage - Tortoise or something like that - wasn't half bad in that regard either...
The only one made is at bovington and its one big mofo: http://www.armourinfocus.co.uk/a39/index.htm

British AFV designers at the time seem to have been vicitims of something like penis envy when it came to big tanks, since they also came up with the Conqueror as a IS3 killer http://www.armourinfocus.co.uk/fv214/index.htm Quite a nice looking vehicle but you have to say the (medium weight) Centurion was a better tank all round.