The Archbishop of Canterbury has discovered he is the illegitimate son of Sir Winston Churchill's private secretary.
The Most Reverend Justin Welby believed his father to be Gavin Welby, a whisky salesman and son of a Jewish immigrant who was married briefly to his mother, Jane. But the Telegraph pieced together evidence suggesting Archbishop Welby's father was Sir Anthony Montague Browne, who served Churchill in Downing St and in his retirement.
After the newspaper discussed its research with the Archbishop, he took a DNA test. His mouth swabs were compared with hair samples from Sir Anthony and showed a 99.9779 per cent probability they were father and son.
The 60-year-old archbishop said the "revelation" was a "complete surprise", but called it "a story of redemption and hope". The Archbishop's mother, who married again and is now Lady Williams of Elvel, confirmed to her son she had a liaison with Sir Anthony shortly before she married Welby, but neither she nor Welby suspected there was doubt about Justin's paternity.
She said the news had come as "an almost unbelievable shock". Archbishop Welby, an only child, has gained a half-sister, Jane, who is three years older than him.
Lambeth Palace had to check canon law, as men born illegitimately were for centuries barred from becoming archbishops. A little-known change in the law in the 1950s removed that bar, leaving Archbishop Welby safe in his post. The news had not affected his relationship with his mother.
Archbishop Welby met Sir Anthony as a boy, because he was a former Downing St colleague of his mother, who was one of Churchill's personal secretaries.
Sir Anthony was a decorated wartime RAF pilot, seconded to work for Churchill from 1952 until the former prime minister's death in 1965.
He died in 2013, but his widow, Shelagh, had kept personal effects, including hairbrushes, enabling a DNA sample to be obtained.
The Archbishop had dismissed rumours about his paternity because he was born almost exactly nine months after his mother married Gavin Welby.
His 86-year-old mother became a magistrate and a deputy lieutenant for Greater London in a long career of public service.
She said "fuelled by a large amount of alcohol on both sides", she had slept with Sir Anthony "in the days leading up to my very sudden marriage".
Sir Anthony's widow, Lady Montague Browne, a personal secretary to Churchill's wife, Clementine, suspected her husband was Justin Welby's father because of the resemblance between the two.
When Archbishop-elect Welby appeared in news reports, Lady Montague Browne's son from a previous marriage, Paddy Macklin, began discussing with Sir Anthony how uncannily alike they looked. Sir Anthony, living in a care home at the time, confirmed to his stepson that Archbishop Welby might be his son. They spoke in French to avoid being overheard.
Sir Anthony said he would like to meet the Archbishop and Macklin contacted him and asked if a meeting was possible. Archbishop Welby agreed, but Sir Anthony died days after his installation in Canterbury in 2013 and the meeting never took place.
Jane Hoare-Temple, the daughter of Sir Anthony and his first wife, Noel, had concluded there must be a family connection because the Archbishop was "the spitting image of my father".
The Archbishop has not yet met his half-sister, although would like to. Hoare-Temple said she would like to meet the Archbishop.