Khandro
Rule, Britannia!’ was composed by Thomas Arne as part of the sung stage work Alfred, which premiered on 1 August 1740 at Cliveden House, home to Frederick, the then Prince of Wales.
The music was written to celebrate the ascension of his grandfather, King George I, and the birth of his daughter, Princess Augusta.
The plot of Alfred revolved around Alfred the Great, a King who reigned over the Saxons during the years 871 - 899.
Set in 871, the masque tells of the story of how Alfred took shelter on the Isle of Athelney, a village in Somerset, following a defeat from the Vikings.
Towards the end of the masque, Alfred leaves to fight again, and is this time victorious. It is ‘Rule, Britannia!’ which is played to illustrate his win, with Alfred saying “Britons, proceed, the subject deep command, awe with your navies ev'ry hostile land”. In response, the chorus sings ‘Rule, Britannia!’.
Nothing to do with pirate raids, so your 'facts' are nonsense.