The HMS Vanguard was the last battleship to be built by any nation and the only such ship in the Royal Navy never to fire its guns in combat. A surplus of 15-in guns from the two Courageous-class battlecruisers that had been converted into carriers prompted the Admiralty to build a shape based on the cancelled Lion-class design. Unfortunately, numerous work stoppages resulted in the ship being delayed and it was completed only until 1946 by which time World War II was over. Aside from the venerable (but extremely effective) BL 15-in Mk. I guns arranged in four double turrets, the HMS Vanguard incorporated substantial anti-aircraft protection from the start including QF 5.25-in Mk. I dual-purpose guns and Bofors guns. Fire control was also quite sophisticated, and included radar for each different gun type as well as remote power control. Armor was based on the preceding King George V-class and included significant splinter protection and improved underwater armor protection. Propulsion was based on the Lion-class designs and in practice, the ship exceeded the planned top speed of 30 knots. Compared to the KGVs, the HMS Vanguard had considerable sheer in its bow, which made it a very seaworthy ship: during NATO exercises it proved less wet than the US Iowa-class. Despite being the heaviest, largest and arguably the most capable battleship ever built for the Royal Navy, its completion after the war reduced it to a fleet flagship and a royal yacht in post-war service and it was decommissioned in 1960.

The HMS Vanguard entered service in 1946, too late to see action in World War II and used only as a flagship and royal yacht. For around a decade, it was the only active Royal Navy battleship following the decommissioning and scrapping of all existing ships in the late 1940s.