Cameron is Queen's cousin, but from 'wrong side of the blanket'

The old Etonian's Royal connection was uncovered by researchers at Debrett's, the British aristocracy and genealogy bible. Mr Cameron is the great-great-great-great-great-grandson of William IV and his long-standing mistress, Dorothy Jordan.

He is descended from the couple's illicit daughter, Elizabeth FitzClarence - making him the Queen's fifth cousin twice removed, but the findings will do little to help his attempts at portraying himself as anything but privileged.

A spokesman for the MP said: "I know for a fact Mr Cameron is blissfully unaware of this. Journalists seem to know far more about his family history than he does. He hasn't looked into his background, but he's said as a passing joke that he's going to."

However, the Royal expert Baron St John of Fawsley told The Scotsman that Mr Cameron hailed "from the wrong side of the blanket". He added: "It's not that unusual. There are an awful lot of people with that line of descent, because William IV had so many children by Mrs Jordan. In fact, I was friends with one of them and she never made anything of it particularly.

"I'd like to tell you I think it was an amazing revelation, but I fear I don't. I think it is just one of those coincidences."

The former Norman St John-Stevas, Tory leader of the House of Commons from 1979 to 1981, said the revelations would not affect Mr Cameron's chances of becoming the next Tory leader.

The result of the leadership ballot of the party's 300,000-strong membership is due to be announced tomorrow.

Baron St John said: "I don't think its significant one way or another, as I think he is going to win anyway, although it may commend him even further to some in the Tory party.

"[Mr Cameron] is many times removed and from the wrong side of the blanket," he added.

Charles Mosley, the editor-in-chief of Debrett's, said: "We're always interested in important people. We did some preliminary work when he threw his hat in the ring, but this link to the Queen is new."

William IV ruled from 1830 to 1837 and was the last sovereign to sack a prime minister. He had no legitimate heir but fathered ten children by Mrs Jordan, an Irish actress.

Mr Mosley joked that the family connection could be of use should Mr Cameron make it to No10. "It might break the ice to have a bit of a link when the new chap takes over and meets the Queen," he said. "It will allow them to exchange jokes and ask: 'How are you, cuz?'"

However, a spokesperson for Buckingham Palace was less amused, saying: "We wouldn't comment on that."

Mr Cameron's family tree also reveals that the Conservative MP for Witney, Oxfordshire, is a descendant of the ancient Scottish royal house of MacDuff.

Mr Cameron's grandfather, Donald Cameron, was married to Enid Levita, the granddaughter of Sir Alfred Cooper and Lady Agnes Duff. Her parents were James Duff, the fifth Earl Fife and chief of the clan MacDuff, and Lady Agnes Hay. She was Elizabeth FitzClarence's daughter by William George, the 18th Earl of Erroll.