Paddy Roy Bates proclaimed HM Fort Roughs, a former World War II Maunsell Sea Fort in the North Sea off the coast of Suffolk, England, as an independent sovereign state: the Principality of Sealand (pictured).

Paddy Roy Bates
Patrick Roy Bates, self-styled as Prince Roy of Sealand, was a British pirate radio broadcaster and micronationalist, who founded the self-proclaimed Principality of Sealand.
HM Fort Roughs
HM Fort Roughs is one of several World War II installations that were designed by Guy Maunsell and known collectively as His Majesty's Forts or as Maunsell Sea Forts; the purpose of which was to guard the port of Harwich, Essex, and more broadly, the Thames estuary. This 4,500 ton artificial naval installation is similar in some respects to "fixed" offshore oil platforms. It is situated on Rough Sands, a sandbar located approximately 11 kilometres (6 nmi) from the coast of Suffolk and 13 kilometres (7 nmi) from the coast of Essex. Today it is the location and de-facto capital of the unrecognised, self-proclaimed state of Sealand.
Maunsell Forts
The Maunsell Forts are towers built in the Thames and Mersey estuaries during the Second World War to help defend the United Kingdom. They were operated as army and navy forts, and named for their designer, Guy Maunsell. The forts were decommissioned during the late 1950s and later used for other activities including pirate radio broadcasting. One of the forts is managed by the unrecognised Principality of Sealand; boats visit the remaining forts occasionally, and a consortium named Project Redsands is planning to conserve the fort situated at Red Sands. The aesthetic attraction of the Maunsell forts has been considered to be associated with the aesthetics of decay, transience and nostalgia.
Suffolk
Suffolk is a ceremonial county in the East of England, with some of it being part of the East Anglia section. It is bordered by Norfolk to the north, the North Sea to the east, Essex to the south, and Cambridgeshire to the west. Ipswich is the largest settlement and the county town.