Arguably the most important surviving wartime structure in Liverpool is in the basement of Derby House, in the city centre. This was the headquarters of Combined Operations, or more familiarly the Western Approaches Headquarters from which the Allied part of the Battle of the Atlantic was planned and controlled.
The Headquarters was relocated from Plymouth in 1941 at Churchill’s instructions, and it was a logical location given Liverpool’s status as the main wartime convoy port of Britain (1,000 convoys arrived there during the war). Hitler apparently suspected that the control bunker was in Liverpool and the heavy bombardment that the city received is in part credited to the Luftwaffe’s attempts to destroy it.
Within this building the Royal Navy and the RAF worked together to monitor Allied convoys and the enemy “Wolf Packs” of U-Boats in the Western Approaches, the eastern half of the Atlantic Ocean that lies to the west of Britain. The nerve centre was the Operations or Map Room at Lower Basement level where there were up to 50 Wrens on duty 24 hours a day updating position indicators and display boards.
The centrepiece was the large Situation Map showing known or suspected enemy positions, allied convoy locations, escort groups and air patrols. An Aircraft State Board indicated the readiness of RAF Stations to send air support or recorded ongoing air operations. Overlooking this at mezzanine level was the glass fronted office of the Commander in Chief, from which he gave instructions via speaking tube.
Churchill apparently visited regularly. A “hotline” telephone linked to the War Cabinet survives and may have been used by him - it was guarded at all times by an armed guard and is one of only 2 such phones which survive. Other rooms on view include a Cinema, a Projector Room, Switchboard/Signal and Phone Exchange, and a heavily guarded Codes and Ciphers Room housing an Enigma Machine. There was also a Sun Ray Treatment Room to help compensate for the long hours (at least 50 hours a week) staff would spend underground.
The 100 or so rooms covering around 5,000m2 were called the Citadel or Fortress by staff. Extensive reinforced concrete protection was provided including a 2.1m thick roof at Ground Floor level
Details of museum opening hours are available on Liverpool War Museum.