The Archbishop of Canterbury has said a DNA test result revealing the identity of his real father has come as a "complete surprise".

The Most Reverend Justin Welby, 60, has discovered he is the son of Sir Winston Churchill's last private secretary, the late Sir Anthony Montague Browne.

He had believed his father was whisky salesman Gavin Welby, who died in 1977.

His mother, Lady Williams of Elvel, has confirmed she had a "liaison" with Sir Anthony just before she wed in 1955.

In a statement issued through Lambeth Palace, the Archbishop of Canterbury refers to his mother and Gavin Welby's addiction to alcohol while he was growing up.

"As a result of my parents' addictions my early life was messy, although I had the blessing and gift of a wonderful education, and was cared for deeply by my grandmother, my mother once she was in recovery, and my father (Gavin Welby) as far as he was able."

Hair samples

He added: "I know that I find who I am in Jesus Christ, not in genetics, and my identity in him never changes...

"Although there are elements of sadness, and even tragedy in my father's (Gavin Welby's) case, this is a story of redemption and hope from a place of tumultuous difficulty and near despair in several lives."

Archbishop Welby, the most senior cleric in the worldwide Anglican communion, says he discovered the real identity of his biological father in recent weeks.

The Daily Telegraph reports that he decided to take a DNA test after it approached him with research it had carried out into his family's background.

It reports mouth swabs were compared with hair samples from a hairbrush kept by Sir Anthony's widow and showed a 99.9779% probability they were father and son.

The Bishop of Norwich, Graham James, told BBC Radio 5 live when Archbishop Welby decided to take the DNA test his thought had been to disprove the claim.

"It proved quite the opposite and he discovered this for certain just before Easter and then contacted his mother... his first thoughts were for her rather than anyone else," he said.

"Although she knew the history of her relationship with Sir Anthony at the time, she'd always believed, as had Gavin Welby, that they were Justin's parents."

'Events patchy'

Lady Williams, whose marriage to Gavin Welby broke up in 1958, had worked as secretary to Sir Winston during his final spell as prime minister.

In a statement published on the internet she said the news had come as an "almost unbelievable shock".

She said: "Although my recollection of events is patchy, I now recognise 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."

Sir Anthony became private secretary to Sir Winston while he was in Downing Street in 1952. He continued in the role after he resigned as prime minister in 1955 and until Sir Winston's death in 1965.

Lady Williams, who remarried in 1975, says she has not drunk alcohol since 1968.

She added that she had seen Sir Anthony occasionally after her relationship with Gavin Welby ended.

"Although he may have asked how Justin was, there was nothing that gave me any hint that he might have thought he was Justin's father," she said.

Educated at Eton and Trinity College Cambridge, Archbishop Welby spent 11 years as an oil executive, before giving up a six-figure salary in 1987 to train as an Anglican priest.

The decision followed a personal tragedy in 1983 with the death of his seven-month-old daughter, Johanna, in a car crash.

In 2002, he became canon at Coventry Cathedral, before serving as Dean of Liverpool Cathedral and the Bishop of Durham. He succeeded Rowan Williams as Archbishop of Canterbury in February 2013.