Down Street was once part of the Great Northern, Piccadilly & Brompton Railway (now known as the Piccadilly line) and stood between Hyde Park Corner and Green Park. After these two stations expanded its use as a tube station became redundant and it was closed in 1932.
It became active again in 1938 during the build up to WWII, the Railway Executive Committee (REC) used it as a bomb proof HQ to house 40 staff during air raids and bombings over London.
There’s only one entrance/exit to the outside, not great in case of fire.
Ventilation was key, especially so Churchill and other execs could smoke in the underground HQ!
Old signage showing the direction of the trains
The platforms were turned in to corridors as part of the REC HQ, doesn’t look much like a tube station anymore.
Interesting the REC architects decided to paint over the original tile works, apparently the “yellow paint” made it more homely for those working 12 hour shifts underground.