Only info I could find was from sub brit

Prior to the outbreak of World War 2 in 1937, proposals were made for a protected joint service HQ in the dry ditch near to Hamoaze House consisting of a single storey structure with a 20 ft concrete and shingle overburden.

By 1939, this plan had been widened to provide an Area Combined HQ (RN & RAF) at the following locations:

C in C Plymouth at Mount Wise
C in C Portsmouth at Fort Southwick
Flag Officer Rosyth at Pitreavie Castle
C in C Nore at HMS Pembroke (post war HMS Wildfire)

These HQ's, built to withstand a direct hit by a 500lb bomb, would house the Naval and Air Force commanders together with an army representative. Also accommodated, would be the Fortress Defence HQ (Coastal Artillery) and Air Defence HQ (Anti Aircraft Artillery)

Construction began in 1939 at Mount Wise on the previously chosen site in the dry ditch, but the plan was now for a two storey structure. As an interim measure, a temporary combined HQ was set up in Eggbuckland Keep, an early fortification in northeast Plymouth, together with the Fortress Defence HQ.
At Mount Wise this resulted in the construction of a series of underground tunnels beneath the lawn of Admiralty House by 695th Artisan Works, 172nd & 178th Tunnelling Companies, RE and 99th & 828th Pioneer Companies, PC.

Blasting began on 15th December 1942 (disturbing the C in C in the adjacent Admiralty House) however technical problems and some minor subsidence of the Admiralty House lawn, temporarily stopped work during March 1943. Work was recommenced on construction and fitting out until the spring of 1944 when the tunnels finally became available.

Following the successful Invasion of Europe and the cessation of hostilities the main
Bunker continued as HQ C in C Plymouth.At the end of the war, No 15 Group, RAF Coastal Command was disbanded on 1st April
1945 and when the second and last C in C, Western Approaches, Admiral Sir Max Horton retired on 15th August 1945. Western Approaches ceased to exist as a separate command with the function, if not the title, returning to the C in C Plymouth. The Tactical School also closed.

On 4th April 1949 NATO was formed, one result of which, was the UK, C in C, Plymouth. becoming double hatted as NATO, C in C, Eastern Atlantic. Which roughly corresponded to the old western approaches area.

In 1951, while the C in C, Plymouth and his staff were fully occupied implementing the new NATO commitments, Captain G Roberts. RN, the officer responsible for the setting up and running of the Western Approaches Tactical School at Exchange Buildings, adjacent to Derby House, was sent for, to evaluate, update and re-organise the Mount Wise HQ, now entitled 'Maritime HQ, for its new expanded duties.

In 1955 some blast protection was added to the entrances and ventilators.

We met our guide at 1pm friday and headed off to the bunker

Plan of the bunker

once through the bunker we then headed down into the ww2 tunnels blasted out of the rock below

some of the rooms off the tunnels were very large

This the WW2 generator block now a substation, the vents you can see in the sid are at eves level in the roof, it was designed to withstand a direct impact frm a 1000 pound bomb

Loads more pics in here, thanks for looking