A fall in customers using the London Underground in 1934 saw Brompton Road station removed from the Piccadilly line and shut down. The station, nestled in an exclusive corner of central London between Harrods and the Victoria and Albert Museum, lay unused for many years - until the Second World War.
Revived as an anti-Luftwaffe command centre, the building was taken over by what was then the War Department and used to control anti-aircraft batteries to protect London from air raids.
Now the slice of the capital's history is put on the market by the Ministry of Defence.
Today the only remnants left of building's military past are a map showing London's anti-aircraft battery areas, ammunition signs and a weapons rack.
– MoD surveyor Julian Chafer
Although I'm not a military historian, I imagine that down here it would been the same sort of thing as you see in wartime films.There would have been maps on the walls, there would have been perhaps an operations table and perhaps a scale model of part of the city, actually physically moving scale models about with the anti-aircraft batteries so people could envisage exactly where they were in the city.
The building is expected to command a high price when the opportunity to bid is opened up to buyers in September.Mr Chafer said: "It's in a prime location, we've got (Grade II*-listed) Brompton Oratory next door, Harrods just down the street, so - subject to what planning authorities say - I think it is likely to be a residential development above ground.
"Quite what happens down here with this site is anybody's guess."There could be things like secure storage for documents but there would have to be quite a bit of work down here to make it safe to bring power down and actually bring people down below ground and back up safely."But I'm sure there are specialist developers out there that would find something to do with this part of the site."