In 1968, British workmen entered what Bates claimed to be his territorial waters to service a navigational buoy near the platform. Bates declared the independence of Roughs Tower and deemed it the Principality of Sealand. Despite having the necessary equipment, he never began broadcasting. Bates intended to broadcast his pirate radio station – called Radio Essex – from the platform. On 2 September 1967, the fort was occupied by Major Paddy Roy Bates, a British citizen and pirate radio broadcaster, who ejected the competing group of pirate broadcasters. Roughs Tower was occupied in February and August 1965 by Jack Moore and his daughter Jane, squatting on behalf of the pirate station Wonderful Radio London. The Maunsell Forts were decommissioned in the 1950s. The facility was occupied by 150–300 Royal Navy personnel throughout World War II the last full-time personnel left in 1956. This is approximately 7 nautical miles (13 km) from the coast of Suffolk, outside the then 3 nmi (6 km) claim of the United Kingdom and, therefore, in international waters.
The fort was towed to a position above the Rough Sands sandbar, where its base was deliberately flooded to sink it on its final resting place. It consisted of a floating pontoon base with a superstructure of two hollow towers joined by a deck upon which other structures could be added. In 1943, during World War II, HM Fort Roughs (sometimes called Roughs Tower) was constructed by the United Kingdom as one of the Maunsell Forts, primarily to defend the vital shipping lanes in nearby estuaries against German mine-laying aircraft.