The new building, completed in 1939, served as the operational headquarters of London District throughout the Second World War.

[3] The structure went on to be occupied by the Security Service (MI5) in 1945; by 1969, when Stella Rimington arrived, it was "dreadfully run down....the inside had not been painted in an age..."[4] The headquarters of MI5 remained at Leconfield House until 1976, when it moved to 140 Gower Street.

[3] The building, which has since been substantially rebuilt, is now occupied by various businesses including that of Robert and Vincent Tchenguiz.

[5] In May 2020, Robert Tchenguiz submitted plans to Westminster City Council to convert the building into a 65-bedroom private members' hotel.

[6] The submitted plans were refused permission by the Council, and Tchenguiz's subsequent appeal against that decision also failed.