Down Street station was used as Winston Churchill’s wartime headquarters during the Second World War.
The station was on the Piccadilly line between Green Park and Hyde Park Corner. It opened in 1907 but closed to passengers in 1932 because nearby stations offered more convenient service. Its platforms and station buildings were later adapted for wartime use.
During the Second World War, the Railway Executive Committee used the protected site, and Churchill’s War Cabinet occasionally operated from facilities associated with the station. The underground rooms provided a secure alternative to offices exposed to bombing, although Churchill more famously used the Cabinet War Rooms in Whitehall.
Down Street is often grouped with Aldwych and Brompton Road as a disused Tube station with wartime associations. Those stations had different uses, so they are not interchangeable answers.