During 1937, with the threat of war imminent, an exchange of letters between the Admiralty, Air Ministry and the War Office resulted in a policy for the provision of protected accommodation at the four main naval ports at Plymouth, Portsmouth, Chatham and Rosyth. It was decided that it would not be practicable or desirable to re-locate the Military HQ’s to the coast so a small military liaison staff was allotted to each of the proposed HQ’s which the Admiralty and Air Ministry now proceeded to plan and build.
The protection against air attack was particularly pertinent for the Navy at Chatham. During the later stages of WW1 on the night of 3rd September 1917, when 900 men were sleeping in the drill shed at the barracks of HMS Pembroke, 4 German Gotha bombers carried out the first night air raid on the UK. One of the planes dropped two 50 kg bombs through the glass roof of the drill shed killing 130 with 88 seriously injured. It was the largest single loss of life due to air raids in WW1. Large underground shelters were dug into the wall of the barracks before WW2 began.
The plan to build these Area Combined Headquarters (ACHQ’s) involved the location of the Air Officer Commanding (AOC) No 15 Group, RAF Coastal Command with the naval Commander in Chief (C in C) Plymouth and Western Approaches at Mount Wise in Plymouth (HMS Drake). AOC No 16 Group, Coastal Command was located with the C in C Nore at Chatham (HMS Pembroke). Pitreavie Castle was to house the naval Flag Officer (FO) Rosyth (HMS Cochrane) and the AOC No 18 Group, Coastal Command.
The naval C in C Portsmouth (HMS Victory) was to relocate alone at Fort Southwick on Portsdown Hill. His area of command was covered by both No 15 (later No 19) and No 16 Groups. No 17 Group, Coastal Command at Gosport had a training role and no area responsibility. In August 1938 HQ Coastal Command moved from Wykeham House, Lee on Solent, Gosport to its new location at Eastbury House in Northwood, northwest London and subsequently in 1943 into its protected HQ. This site then went on to become HMS Warrior and later the Permanent Joint HQ (PJHQ).
Following the outbreak of hostilities and the occupation of northern Europe, adjustments were required in the above arrangements. In June 1940 the naval command at Plymouth was split, with a new C in C Western Approaches (HMS Eaglet) and the AOC No 15 Group moving north to Liverpool and into protected accommodation in Derby House in February 1941. The existing C in C Plymouth remained at Mount Wise where he was joined by the AOC of the newly formed No 19 Group to cover the South Western Approaches.
The design, size and construction of the five ACHQ’s are all different
