The recently-selected Lib Dem candidate for Mayor of London will divulge details of his first gay sexual encounter in his memoirs.

Brian Paddick’s autobiography Line of Fire is not due for publication until April 2008, just weeks before the election.

Already there is widespread speculation about the contents of the book, which will almost certainly contain heavy criticism of London’s Metropolitan Police commissioner Sir Ian Blair.

Mr Paddick was the UK’s most senior out gay officer until he stood down from the Met in May.

He clashed with Sir Ian over when the Met knew that they had shot an innocent man at Stockwell tube station on July 22nd 2005.

Sir Ian insists that he did not know Brazilian Jean Charles De Menezes was not a suicide bomber until the next day.

Mr Paddick gave evidence to an independent investigation that suspicions were raised almost immediately.

The Times reports that in his book, Mr Paddick, who rose to the rank of Deputy Assistant Commissioner in the Met, had his first homosexual sex with a fellow officer, described as “an attractive male PC,” in a police lodging house in north London.

He describes the “turmoil” he went through after the experience, and frankly discusses his affairs with other women, his marriage and his attempts to repress his homosexual desires through religion.

Last week 49-year-old Mr Paddick won 73% of the first preference votes in a ballot of London Lib Dem party members to become their candidate for Mayor.

He faces incumbent Ken Livingstone and Tory candidate Boris Johnson in next May’s election.