Prince Charles.
Because she married the heir to the British throne.
She married the heir to the throne of the UK.
Prince Charles, the Prince of Wales, married Lady Diana Spencer on the 29th of July, 1981.
Princess Diana became a princess after she married prince Charles. The prince of Wales and heir to the throne of England.
Princess Diana Charles , was the late wife of Prince Charles the heir to the english throne.
Because Prince Charles was - and still is - the Prince of Wales when she married him. Her name was never Princess Diana. He correct title was Diana, Princess of Wales.
There is no event that would not have taken place if there was a female heir to the british throne. Except perhaps the wedding of Charles and Diana. Also for conspiricy theorists Diana would have not been assassinated?
If Charles and Diana had remained married and childless, the heir to the throne would have been Prince Andrew, and if Andrew did not have male issue, the next-in-line would have been Prince Edward.
to produce a son as heir to the throne
Prince William
Prince William - married Kate Middleton.