Admiralty House is a substantial building at Mount Wise, Devonport, Plymouth.[6] In 1939-41 a partly subterranean complex of buildings was constructed in the grounds of the house, within the ditch of the old fortifications, to serve as a combined RN/RAF headquarters for maritime operations; similar Area Command Headquarters were constructed at the same time close to the Royal Naval Dockyards at Portsmouth, Chatham) and Rosyth.[8] The headquarters were expanded during World War II by a series of tunnels, known as Plymouth Underground Extension (PUE), which formed a sizeable bomb-proof bunker complex under the garden of Admiralty House; it could be accessed from Richmond Walk, Blagdon's boatyard and Hamoaze House as well as from the headquarters building itself.[6] After 1969, Admiralty House became the home of the Flag Officer, Plymouth until that post was also disbanded in 1996.[6] The house was marketed for sale as a potential hotel in 2014 and much of the surrounding site was adapted for residential use in 2015.