Here's a wikipedia entry about the HMS
Vanguard which Sailor Steve mentioned, Britain's largest and last battleship. She was a 40,000 ton warship with 15" naval rifles. But due to the priority given other construction she was not completed until 1946 and missed the war.
http://en.wikipedia.org/wiki/HMS_Vanguard_%2823%29
She was scrapped in 1960, having never seen combat. Some feel her guns would have quite handy for shore bombardment purposes had she still been about during the Falklands conflict of 1982.