It was a romantic friendship, a love expressed in the manner of Oscar Wilde to his “dear boy” Bosie, and for it, John Mortimer, the future celebrated author and dramatist was sent down from Oxford in disgrace.

The letters to a schoolboy that were enough to incriminate Mortimer in the eyes of the academic authorities were destroyed. Mortimer never spoke publicly of the affair again.

Now Valerie Grove, his official biographer, has pieced together the story from a handful of letters in the archives of Leeds University Library.

Mortimer told The Times yesterday that the experience was “buried deeply in the past”. But he added: “I don’t mind it being out in the open now.”

In correspondence from Mortimer to a fellow undergraduate, Michael Hamburger, there was a reference to an unnamed scandal. “I am terribly sorry to have got you into all this,” Mortimer had written in August, 1942. “I was a bloody fool.”

A distinguished poet, Professor Hamburger later wrote a discreet account of the incident in his memoirs. He had described how a friend had “invited two boys still at his public school, to Oxford, where we all met”.

Another friend, “who I had taken to be heterosexual, conceived a violent passion for one of the two boys. In one of his letters to the boy, which had been intercepted by the boy’s headmaster, my friend had written: ‘Michael Hamburger sends his love’. In the middle of the vacation I was summoned to the Dean of Christ Church and put through a gruelling interrogation.”

His friend was John Mortimer, the schoolboy was Quentin Edwards, a sixth-former at Bradfield College. In the spring of 1941 they had been punting together on the Cherwell and attended a ballet. Mortimer had given him a copy of Shakespeare’s sonnets, they had planned to meet again. In the meantime, Mortimer had written Edwards a series of florid letters.

Mr Edwards, 80, a distinguished, retired circuit judge, described them as “the kind of letters you’d hate anyone else to read, addressed to ‘My Dear Boy’, couched in rather romantic terms, like Oscar Wilde’s letters to Bosie, with amusing jokes about undergraduates masturbating in their rooms.”

Sixty-five years later, both insist that it was a youthful crush, rather than a physical relationship. “We’d been to single-sex public schools where people form romantic friendships which are not really quite homosexual,” said Mr Edwards.

His housemaster had discovered the letters in his desk and showed them to the headmaster. Both men assumed that the two were having a sexual relationship. Edwards was told not to return to school the following term. The headmaster added that, in his opinion, the letters were of no literary merit. “You needn’t think this man’s got any real ability,” he said.

The Dean of Christ Church college, where Mortimer was lodged, was also informed. Yesterday, Mortimer said: “I don’t think I was sent down. I was invited not to come back. It was hysterical, the reaction. My father was very understanding and now everybody says what a nonsense it was.”

Professor Hamburger feels it was a grave injustice: the same college ignored the activities of a homosexual don who would offer freshmen “instructions on the facts of life”.

As a barrister in 1977, Mortimer would defend Gay News on a blasphemy charge. His 1971 play, Bermondsey, contained the first gay kiss to be performed on a West End stage and critics praised him for his groundbreaking treatment of homosexuality.

Yesterday, Mortimer said the affair had “not featured very largely in my mind . . . but I have always battled against all sorts of hypocrisy”.

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