Admiralty Citadel.

The Citadel was constructed between 1940 and 1941 as a bomb-proof operations centre for the Admiralty at a time when London was being heavily bombed and there was an imminent threat of a German invasion. The Admiralty was already being hit by the Luftwaffe. During the night of 16 April 1941 three bombs landed direct hits on the Admiralty, damaging the Board Room and part of the south front adjoining Horse Guards Parade.