The black bra being dangled in front of Jeffrey Archer’s face told its own story. He had been well and truly caught out. But this was one public humiliation that the novelist could happily laugh off. For when Oxford historian Julie Summers delved in her handbag before triumphantly producing a bra, it was only to bring to her fellow writer’s attention the smallest of slips in his new book, Paths of Glory.

The book’s hero on his wedding night, simply could not have fumbled with the strap of his bride’s bra, because on the eve of the First World War no woman in England would have been wearing one. They were neither available, nor even thought of, until many years later Ms Summers explained to a highly amused Oxford Literary Festival audience.

Given that his new book, inspired by the true story of the legendary climber George Mallory, had involved Lord Archer in an unusually high level of research, it was ironic that he should have erred in the bedroom, normally safe ground for this novelist.

Mountaineering and real-life historic heroes, however, would seem an altogether different matter, and his decision to provide a fictional account of the climber who may well have been the first man to reach the summit of Everest has certainly seen Lord Archer move on to unfamiliar territory.

At the age of 68, Jeffrey Archer would be hard pressed to think of many living people who can match the same dizzy heights, followed by an almost pre-ordained fall, as himself.

But it seems that in George Mallory, he has found not only a hero with whom he can identify, but one he clearly loves.

He certainly takes pride in the fact that, by giving a fictionalised version of the Mallory story, he will make millions more aware of one of the ultimate English adventurers, who, for some reason, has never secured the kind of fame bestowed upon Captain Scott and Shackleton.

Making his third and final attempt to conquer Everest, George Mallory perished in 1924 with his climbing partner Sandy Irvine, a 22-year-old Oxford student. To this day nobody knows whether they died having been the first men to stand on the ‘Roof of the World’ almost 30 years before Hillary and Tenzing.

Lord Archer was in Oxford on Friday to tell how his and Mallory’s paths came to cross. Never being a man lacking in confidence, he readily agreed to appear alongside Ms Summers, who apart from being a leading authority on the doomed expedition, also happens to be the great niece of Irvine, about whom she has written extensively.

Setting the bra removal aside, it came as no surprise to find the historian hardly relishing the story being given the full Jeffrey Archer treatment, while finding no shortage of factual errors from a man (to borrow his wife’s phrase) with “a gift for inaccurate precis”. But for those of us who have carefully followed the carnival of risks, bluff and naked ambition that has made up much of Lord Archer’s life, Paths of Glory shows the novelist in something of a new light.

It turns out that Lord Archer only became fully aware of the Mallory/Irvine story about 12 years ago, as he explained to me shortly before his literary festival appearance in the Newman Rooms.

Lord Archer said he had been urged to look at the story by his friend the late Chris Brasher, the man who founded the London Marathon and who, with Christopher Chataway, had set the pace for Roger Bannister to break the four-minute mile at Iffley Road.

“He told me over lunch it made a better story than Shackleton and Scott, much more romantic and much more fascinating because it had such a mystery to it. Here was a man who had got to 630ft from the top of Everest and nobody knows what happened to him. He had been to Everest three times, he was the greatest climber of his day, he was 37-years-old and he knew it would be his last attempt.

“Chris said, ‘you are the man to write it, Jeffrey. You love heroes, you love sport, you will love the mystery element of it’.”

But it was only after Brasher’s death in 2003, that he took the advice to heart. He now sees Paths of Glory as a tribute to both Mallory and his old friend’s memory.

Mallory was regarded as the best-looking man of his age, married to a famous beauty, a friend of the great men and women of his day and was a risk taker on a heroic scale. So, did he, Lord Archer, see anything of himself in Mallory?

“A fair question,” he replied, without a hint of self-consciousness.

“I’ve never been up a higher mountain than Ben Nevis, which I climbed at the age of 64. But I married the most beautiful woman at Oxford University and the cleverest.”

And he has no doubts that he would have been like Mallory, quite prepared to risk everything in a final desperate throw of the dice.

Who can doubt it, given the level of recklessness that landed him in prison for two years for perjury?

His prison diaries earned him new respect as a writer, but did prison change him as a man?

“I am aware of how privileged I am and of how lucky I have been. I get up every single morning and say to myself, ‘you are a lucky bastard’. I think I’m also calmer about other people’s mistakes when things go wrong.”

The man who could count himself as a close friend of two Prime Ministers is soon speaking with obvious affection about another pair of friends, both murderers. One, a victim of sexual abuse over ten years from the age of six, killed the paedophile who had ruined his childhood.

Lord Archer was drawn to the other convicted killer while in prison on discovering that he was learning to read and write. “I went to his BA degree ceremony six months ago. He is now doing an MA and he is preparing for a PhD. Prison taught me you must not just bundle people up and put them under one label.”

He disclosed that he recently had lunch with the Conservative Chief Whip in the House of Commons but advises not to read anything into that. “I’m nearly 70. Those days are gone for a lot of reasons. It is a whole new generation. Cameron will become Prime Minster, although I say that advisedly. Nothing is certain in politics.”

So how does he compare David Cameron with Thatcher and Major, whom he served for more than 20 years.

“I’ve only met him a few times. He is charming and easy to speak to. It is easy to make statements, but unless you have been in the office and see how he delegates and commands his own people, you are foolish to make a judgment.”

He prides himself on his charity auctions, including one for the Oxford Cancer Hospital, which raised £2.2m last year. Quite an accomplishment for a man, who will tell you that 50m people in India have read one of his books.

If he misses the whiff of power, he surely must sleep easier knowing that his bête noire, the investigative reporter Michael Crick, is no longer digging away for another great Archer story.

“I bore them all now,” he said. “They fall asleep in front of me. What is Crick doing now? Is he still working for Newsnight?”

But Crick is right. Lord Archer never does anything ordinary or dull. He is soon talking about Paths of Glory being turned into a film, directed by Bruce Beresford (director of Driving Miss Daisy), with Daniel Day-Lewis apparently interested in playing Mallory.

“I hope there will be an announcement in a few weeks’ time,” said Lord Archer, who has already written a script. “But I am listening to my son, who said, ‘don’t believe it until you’re eating the popcorn’.”

His books have spawned three mini-series, but, surprisingly, never a motion picture.

Like the book, the film version of Paths of Glory, would certainly have snobbery at its centre, for Lord Archer makes much of the fact that Mallory’s friend and rival, the hugely experienced George Finch, was dropped from Mallory’s final expedition by the Royal Geographic Society on the grounds that he was Australian and divorced.

Taking the strongly-built Oxford student Sandy Irvine with him was a massive mistake, argues Archer, given that Irvine had never previously climbed much over 5,500 ft.

“Irvine may have been responsible for Mallory’s death, simply because he lacked experience. Not his fault, I should strongly point out.”

Snobbery was something, he says, entirely absent during his own time at Oxford University, where he arrived in 1963 to do a diploma in education.

He still regards his time at Brasenose College, where he became an athletics Blue and international runner, as his happiest.

“My wife was a don there and my son was an undergraduate. Because the three of us have connections I feel I would like to do something positive. I’m not entirely sure what it is yet, but they are coming to see me. I’m at that terrible age.”

But it is like Mallory and any other seriously ambitious climber would have told you, the coming down is always harder than the ascent.