A British ex-army major seized an abandoned WWII sea fort off the English coast in 1967 and declared it a sovereign nation. It has its own currency, passports, and national anthem. It has also survived an armed coup.
HM Fort Roughs was an anti-aircraft platform built by Britain during World War II and abandoned in 1956. It sits on a concrete pontoon roughly 11 kilometers off the Suffolk coast, beyond what was then Britain's three-nautical-mile territorial limit — technically in international waters.
In September 1967, Paddy Roy Bates — a former British army major turned pirate radio operator — seized the platform from competing broadcasters and declared it the independent Principality of Sealand. He styled himself Prince Roy, his wife Princess Joan, and issued a national flag, currency, stamps, and passports.
When British workmen serviced a nearby buoy in 1968 and Michael Bates (Paddy's son) fired warning shots, the case went to a British court — which ruled it had no jurisdiction because the platform was outside territorial waters. Bates framed this as de facto recognition of Sealand's sovereignty. He had the ruling framed.
In 1978, while Paddy was in Austria, a German businessman named Alexander Achenbach — who claimed the title of Sealand's Prime Minister — hired Dutch and German mercenaries and stormed the platform by helicopter. Michael Bates retook it with a helicopter-borne counterassault and held Achenbach for treason. Germany sent an actual diplomat to negotiate his release, which Bates also framed as recognition.
In 1987, Britain extended its territorial waters from three to twelve nautical miles, placing Sealand legally within UK jurisdiction. Britain has not acted on this. Sealand continues to operate, selling noble titles ('Lord of Sealand' for around £30), hosting an offshore internet server, and maintaining nominal sports teams.
Paddy Roy Bates died in 2012 at 91. His son Michael runs the family fishing business in Suffolk while nominally governing a platform with approximately one permanent resident. The Pirate Bay attempted to buy Sealand in 2007. The asking price at one point was €750 million.