hms lion (1939)
Lead ship of her class, which were planned but cancelled in early WWII. With this class the UK finally discarded all treaty restrictions. Originally planned as enlarged 16in gun version of the King George V the class went through many iterations, the last of which were planned during the late 1940s.
This is the entry about the unbuilt British battleship, for the battlecruiser that was actually constructed pre-WWI... well danbooru doesn't actually have a page for her yet.