The Archbishop of Canterbury, Justin Welby, has said it is a "complete surprise" to discover the identity of his biological father is not as he had always thought.
Following an investigation by The Telegraph, a DNA test revealed that the archbishop's father was Sir Anthony Montague Browne, and not whisky salesman Gavin Welby, who was briefly married to his mother, and died in 1977.
Montague Browne was once a private secretary to former prime minister Sir Winston Churchill during his time in Downing Street, where Welby's mother also worked.
In a statement, now-remarried Lady Jane Williams of Elvel said the results of the DNA test were an "almost unbelievable shock", but confirmed that "during the days leading up to my very sudden marriage, and fuelled by a large amount of alcohol on both sides, I went to bed with Anthony Montague Browne".
"It appears that the precautions taken at the time didn't work and my wonderful son was conceived as a result of this liaison."
Welby said it was a "complete surprise" to discover that Montague Browne was his father after being urged to take a DNA test based on rumours around his father's true identity.
The archbishop has described having had a "messy" early life as a result of his parents' alcoholism, but said in a statement that he was "enormously proud" of his mother, who has been in recovery since 1968.
Jane and Gavin Welby were married in 1955, but separated in 1958.
"My own experience is typical of many people. To find that one's father is other than imagined is not unusual. To be the child of families with great difficulties in relationships, with substance abuse or other matters, is far too normal," Welby said in a statement.
Welby, who is the most senior figure in the Church of England said that the revelation had been a complete surprise, but added, " I know that I find who I am in Jesus Christ, not in genetics, and my identity in him never changes.
"Even more importantly my role as Archbishop makes me constantly aware of the real and genuine pain and suffering of many around the world, which should be the main focus of our prayers."
An ancient canon law once dictated that a child born out of wedlock was unable to become archbishop, but it was removed in the 1950s.
He told The Telegraph that "I wasn't in any way upset… and I remain not upset," about the news, and that his relationship with his mother remains unaffected, praising her for "always looking reality straight in the face".
Welby's presumed father, Gavin, was a Jewish immigrant, and Welby is said to be disappointed that he is no longer the first Archbishop of Canterbury to have Jewish blood.
While Montague Browne died in 2013, the paternity test was possible after his widow, Shelagh, donated her late husband's hairbrushes, which still contained traces of his hair.
Welby had met Montague Browne as a child as a result of his mother's work connection to him.
Following the news, Welby has gained a half-sister, Jane.