In 1967, Paddy Roy Bates declared HM Fort Roughs, an abandoned British anti-aircraft platform off the coast of Suffolk, as the independent Principality of Sealand. While the UK largely ignored the self-proclaimed sovereign, a bizarre crisis unfolded in August 1978. Alexander Achenbach, a German lawyer claiming to be Sealand's Prime Minister, hired Dutch and German mercenaries to invade the platform while Roy Bates was away.
They took Bates' son, Michael, hostage. However, Michael and local supporters managed to recapture the platform, holding the mercenaries captive as prisoners of war. Most mercenaries were quickly repatriated, but Achenbach held a Sealand passport and was formally charged with treason against the micronation, facing a $35,000 fine.
Germany requested the United Kingdom intervene, but the British government declared the fort was outside its territorial waters and had no jurisdiction. Desperate to free its citizen, West Germany dispatched a diplomat, Christoph Rosenberg, from its London embassy directly to Sealand to negotiate Achenbach's release. After weeks of negotiation, Roy Bates released Achenbach and claimed that Germany's direct diplomatic mission constituted legal de facto recognition of Sealand's sovereignty.
Although Germany officially denied this interpretation, the incident remains one of the most extraordinary legal anomalies in modern international law.