In 1943, during the Second World War, the United Kingdom constructed several naval forts named Maunsell Sea Forts to monitor and report German mine-laying aircraft that might be targeting the estuaries that were part of vital shipping lanes. At the time of its construction, the forts were on international waters. The structure consisted of a floating pontoon base with a superstructure of two hollow towers joined by a deck upon which other structures could be added. The facility was called Roughs Tower, and was occupied by 150–300 Royal Navy personnel throughout World War II. After being abandoned by the Royal Navy in 1956, this artificial island on the high seas was occupied by a pirate radio station before Paddy Roy Bates evicted the illegal tenants and became a squatter himself.