In 1942, during World War II, the British government set up a small base in the North Sea just outside British territorial waters (at the time). After the war, the fort was abandoned, but, in 1967, Roy Bates, a pirate radio broadcaster, claimed it as the Principality of Sealand. The British government’s stated view is that Sealand is within British jurisdiction. Sealand generally is classified as a micronation (a nation project set up by an individual or group, and has no international recognition.)
As pertaining to the anthem, it was composed by London composer Basil Simonenko in conjunction with the governing Bates family, and has no words. The title of the anthem is also the motto of Sealand.
Special thanks to: Paweł Ciupak for the music file.