The guest list at the wedding of Prince Charles and Lady Diana Spencer on 29 July 1981 included many members of royal families from across the world, republican heads of state, and members of the bride's and groom's families. As Prince Charles was heir to the British throne, the event was automatically deemed a "state occasion", formally requiring the invitation of many foreign heads of state; in addition, the marriage of the prince, who remained a bachelor until the age of 32, to the 20-year-old Lady Diana drew much attention from across the world. The guest list for the wedding, which took place at St Paul's Cathedral in London, included 3,500 people.