The building, which has a prominent mansard roof, was completed around 1924, when it became the main operating base for the Secret Intelligence Service.[1][a] In 1925, the Government Code and Cypher School co-located within the building, although it was on a different floor to the Secret Intelligence Service.[2][b] GC&CS moved out to Bletchley Park in August 1939.[3]
During the Second World War it had a brass plaque identifying it as the offices of the "Minimax Fire Extinguisher Company".[1] Sir Stewart Menzies, Chief of the Secret Intelligence Service, had access to a tunnel, which connected 54 Broadway to his private residence in Queen Anne's Gate.[4] Kim Philby, who worked in the building during the war, described it as "a dingy building, a warren of wooden partitions and frosted glass windows...served by an ancient lift."[5]
The Secret Intelligence Service moved out to Century House in 1964.[6] During the 1990s, the building was used by the project team for the Jubilee Line Extension to the London Underground.[7]
