The celebration of the Sovereign's jubilee years really began in the long reign of King George III. The beginning of the fiftieth year of his reign, on 25 October 1809, was marked both in Britain and the Colonies. The King and other members of the Royal Family attended a private service in Windsor and a grand fete and firework display at Frogmore. In London the Lord Mayor and Corporation processed to St Paul's Cathedral for a service of thanksgiving before holding a dinner at the Mansion House.