As a main Naval base, a WW2 Headquarters in Plymouth was necessary. It was sited within the grounds of Admiralty House, a 19th Century house within the garrison area of Plymouth docks, and became known as Mount Wise. Construction of the main, two level sunken concrete bunker began in 1939 but the site was extended with a series of underground tunnels in 1942. This was known as the Plymouth Underground Extension, and it is located under the grounds of the house. The main bunker area was fitted and operational with many rooms, and remained in MOD use throughout the Cold War, until it was decommissioned in 2004. It is obvious, however, that the tunnels were abandoned long before this time, although some operational equipment still remains within them. The bunker is currently being refitted as a secure storage data centre, and fortunately, the renovation plans seem to be sympathetic with the site's history.
Many thanks to the owners for allowing a visit to this facility, and Mr John Sar for arranging.
Entrance to the bunker in the C19th Ditch