Is he serious? Two minutes later, he declares: "There is a big hole at the centre of Anglicanism - its authority. I don't think it's a Church; it's more of a religious society." This is the most hurtful criticism that one can make of any Church: to say that it is not a Church.

In fact, his book, Anglican Difficulties: A New Syllabus of Errors, is one of the most ferocious assaults ever launched on the Church of England. It is all the more deadly because its author is not a traditionalist quote-merchant, but a leading Church intellectual.

A former Reith lecturer and Dean of Peterhouse, Canon Norman is an ecclesiastical historian with the long face and high cheekbones of a Tudor churchman. He speaks fast and quietly, polishing his dry words as he speaks, so that his prose and conversation are almost indistinguishable. He commits thoughts to paper that colleagues might let slip only in the senior common room after dinner.

In Anglican Difficulties, Norman blazes away impartially at all the Church's factions. About the General Synod, he writes: "Every disagreement, in seemingly every board or committee, proceeds by avoidance of principled debate. Ordinary moral cowardice is represented as wise judgment; equivocation in the construction of compromise formulae is second nature to leaders."

Evangelical bishops who trumpet their adherence to Biblical orthodoxy are accused of selling their principles in return for preferment. "Discreetly, behind the twitching curtains of the evangelical bishops' houses, the playing pieces are being set out on the board," writes Norman.

So how can someone who believes that the Church of England is collapsing belong to it?

The answer is that Edward Norman will leave the Church of England when he retires as a member of York Minster's chapter in May. Later this year, he will be received into the Roman Catholic Church by a Cambridge contemporary, Fr Dermot Fenlon, at the Birmingham Oratory. He has started attending Mass in Catholic churches, unobserved in collar and tie.

But there is no mention of conversion to Rome in Anglican Difficulties. Norman stresses that leaving the C of E and becoming a Catholic are "quite independent developments". Like his insistence that his new book is not a criticism of Anglicanism, this point is not easy to grasp, but Norman is insistent.

"Just because the Anglican tub is leaking is not in itself an argument for jumping into another one," he explains. His conversation drips with these aquatic metaphors.

Over lunch in an Italian restaurant near the Minster, he announces: "Anglicanism is going to tip into the sea." He reaches for the bread with a thin smile. "But it will all come out in the wash."

Norman eats a plate of pasta here every lunchtime. "It is my only meal of the day," he says, which is not hard to believe: he is rake-thin and ascetic, a convert in the mould of John Henry Newman rather than GK Chesterton.

This is not an obvious candidate for "Poping". Like Newman, Norman has always been Low Church; when he arrived at York Minister, he had to be helped through the rituals. And didn't he once support women priests?

"I was originally in favour, on rationalist liberal grounds," he says, apologetically. "Now, I'm against it - on the evidence. We were told that a whole dimension to humanity was missing from the ministry, but that enrichment hasn't happened."

What follows is a typical Edward Norman argument, either perverse or original, depending on your point of view.

"Women emphasise caring, relationships, suffering, healing and love. Men are interested in truth, ideas, conflict, sin, wickedness and virtue. Those are caricatures, but there was wisdom in Our Lord entrusting the office of the priesthood to men.

"The priesthood is about teaching, not just conveyance of the sacraments. If you think Christianity is all about love and relationships, then it will disappear in the flood."

He catches my surprised look and shrugs. "I can't think of a way of putting this into words that is acceptable to contemporary culture," he says.

Not that he tries. There is something in Norman's world view to offend everyone: liberals, who imagine that "caring" is an adequate substitute for the rigours of the Gospel; lovers of art and music, who mistake aesthetic sensations for spirituality; Tory-voting country types who enjoy a jolly good sing-song at Matins.

"The number of people who respond to the teaching of the truth is extremely small," he says. "I have friends who come to York Minster who are very good people, even godly, but it's a very conventional, class-based observance."

Class runs through Norman's writings, a legacy of his youthful Marxism. His reputation now is that of a maverick Right-winger, but he says that is wrong: "I have no politics. My only ideology is classical Christianity, without reservation."

In the late 1970s, Norman's broadsides against the trendy Left earned him the label of Margaret Thatcher's favourite clergyman; she even invited him to Chequers. "But there wasn't any meeting of minds," he says firmly.

"Mrs T wasn't - isn't - a very deep thinker. She was the daughter of an alderman who was a Gladstonian liberal, and that was what she was, too. She was looking for an intellectual to give a pedigree to those liberal values. I have admiration for her, and found her personally kind. But I have been appalled by the results of naked capitalism."

His own sympathies are unpredictable. One wonders if Lady Thatcher would still admire him if she had heard his final lecture at York Minster - an appreciation of the oeuvre of gay atheist filmmaker Derek Jarman.

The lecture was extraordinary, not least for the Jarman quotes that Norman included. Jarman on Dr George Carey: "Moon-faced and pudgy, a clerical Bunter, the school bully in a lurex mitre." And on Carey's enthronement as Archbishop of Canterbury: "This is where crap takes you."

The canon chancellor of York Minster quoted these lines as if he approved of them. Perhaps his failure to reach high office in the established Church is not that mysterious.

Norman spent 17 years at Peterhouse, where one of his students was Michael Portillo. "A very hard-working pupil," he recalls. "I never noticed any sexual irregularity in his life."

Most of Norman's time as a Cambridge don was given over to writing studies of (among others) the Victorian Christian socialists and modern Ireland. He was also a participant in one of the most vigorous High Table feuds in recent history, which began when he fell out with the Master of Peterhouse, the late Lord Dacre, over a memorial service for a don who had been caught shoplifting.

Norman thought the man deserved a Cambridge memorial service. Dacre disagreed. As Norman recounts it, Dacre's views do indeed sound unreasonable. (Years ago, when working on a newspaper diary column, I sought Dacre's side of the story. He would only say: "Dr Norman is a s--t.")

After lunch, Norman shows me around the cathedral. "This is a very poor example of the late-Gothic style," he says, his thin arm sweeping dismissively across the widest medieval nave in England. "It was put up on the cheap - the decorative devices are straight out of a stonemason's catalogue."

But doesn't the miraculous, vaulted ceiling help worshippers concentrate their thoughts? "Cathedrals can be a hindrance as well as an aid to faith," says Norman. "They can lead people to luxuriate in emotion. I'd rather they were convicted of their sins."

We pass a statue of the Minster's patron saint, St Peter, holding a key. It's an appropriate image. Soon, Canon Norman will be free of "the ideological chaos of Anglicanism" and in full communion with (as he believes) the successor of Peter. Then will come retirement in Brighton - "And I shall be properly retired," he says.

The reaction of his critics is not hard to predict: "Well, there's one Anglican difficulty out of the way," they will smirk. But others will regret the loss of one of the most profound and unsettling thinkers that the Church of England has produced in decades.

"Catholicism is what I have always believed, though I did not have the wit to realise it," says Canon Norman, gathering his coat around him. "You might call it a shaft of light before the sun sets."

© Copyright of Telegraph Group Limited 2004.