Built in 1870, Fort Southwick was one of the Portsdown Hill forts designed to protect the vitally important Naval harbour of Portsmouth. However, the importance of Fort Southwick increased during the Second World War when a series of tunnels were constructed beneath the Victorian fort. These tunnels were an underground headquarters (UGHQ) for all the armed forces during the planning and execution of Operation Overlord – the Allied invasion of mainland Europe on D-Day, June 6th 1944. At this time there were up to 700 staff working in the UGHQ.
The importance of the UGHQ at Fort Southwick remained during the Cold War. As an HQ and C-in-C Home station, Fort Southwick was known to Soviet intelligence and as a result, a target assessment undertaken by the Joint Intelligence Committee in 1967 anticipated that Fort Southwick would have been heavily attacked with nuclear weapons, probably two 1 – 3 MT air burst detonations.
The tunnels today are used for Airsoft and storage, with hopes that some sections may be restored to their Second World War state.
Location: Nr Portsmouth
Date Of Visit: 06/09/08