WITHIN the first few pages of Robert Runcie, The Reluctant Archbishop, the subject of this biography remembers that a favourite phrase of his unbelieving father's was, "Never trust parsons or policemen." With hindsight he should have added "or biographers."

As Archbishop of Canterbury from 1980 till 1991, Robert Runcie was the head of the established church during a decade which saw the rise of Thatcherism, the Falklands War, the marriage (and its subsequent breakdown) of the heir to the throne, an economic recession, the Middle East hostage crisis (the non-ordained Terry Waite was "Archbishop's Assistant for Anglican Communion Affairs") and the Gulf War.

The role of Archbishop of Canterbury is unique, at once titular ceremonial and pastoral. As far as the day job was concerned, his tenure coincided with a succession of crises over homosexuality the ordination of women and the drift to Rome.

By 1991, as his term of office was drawing to a close (an event he referred to as his "liberation"), three biographies had already been written. But he wanted something more personal as a summing up.

A liberal and somewhat quaint man of humble origins, given to letting his hair down whenever possible (and regularly pilloried - for his efforts on Spitting Image and by the young fogeys of the highbrow press), Archbishop Runcie had in mind something that "scores high marks on readability and breaks with the old- fashioned ecclesiastical melange of letters and documents".

Given the confidential nature of much of what he had to recount, Dr Runcie needed a biographer he could trust. Humphrey Carpenter must have seemed just the ticket. He was the son of the Bishop of Oxford - one of his closest friends - and was author of several prize-winning biographies. But the archbishop perhaps failed to notice that Carpenter's previous subjects were all dead.

What he got was the ultimate in post-modern biography, in which the process is not only visible but central to the finished product the technique devised by Boswell in his Life of Samuel Johnson. What he lost was his reputation.

AS soon as the extracts appeared in the Times (carefully chosen for maximum shock), members of the establishment cried foul.

They are not to be pitied. The scattering of buckshot will merely leave their amply padded bottoms a little stung. The damage to Lord and Lady Runcie, however, is far more serious.

This past week, cloaked in the anonymity of outrage, the establishment has taken its revenge, lambasting him for his betrayal of church, state and monarch (he is a member of the Privy Council and subject to its self-regulatory rule of confidence) and deriding him for his ego-driven naivety.

Tuesday's leader in the Daily Mail called him "a blabbermouth" whose indiscretions confided to a proffered tape recorder have transformed the former Primate of All England into one of the minor comic characters of contemporary history".

Lord St John of Fawsley (formerly Norman St John Stevas, a Tory cabinet minister), who is a high-profile Catholic, has taken a more charitable view, declaring that Lord Runcie was "more sinned against than sinning".

The saddest quote of the week came from Lord Runcie himself, in a postscript to the book. Realising that he had nowhere to run, he wrote: "I have done my best to die before this book is published."

Thank God that suicide was not an option for this man. That we - and future historians - are the richer for Lord Runcie's honest reminiscences is clear.

But from the pitiful suicide of one of his many speech and sermon writers (a revelation in itself), whose aspirations for greatness were never to be fulfilled, to the sad realisation that right from the start Charles and Diana's marriage was a sham, what the book exposes are less state secrets than private secrets, and the misery of life at high table.

During his time in office Lord Runcie presided over a church in decline. This week's shots from the hip may well hasten its death, or at the very least sever the arterial link between church and state.

For while Charles was wittering on about the headaches of life within the stranglehold of an established church, scant thought has been given to the other side of the coin, namely the Church of England being saddled with the monarchy.

Lord Runcie's confessing that he believed "Charles had already given up on the church" was hardly divine revelation. But to have such a fellow hovering on the horizon as future chairman of the board - you may as well call in the bailiffs now.

Then there is that wedding. Any other priest faced with conducting a marriage he knew was not the love match it was dressed up to be would have aired his concern to the couple, and would probably have advised them to call it off.

Add to that the archbishop's knowledge of Charles's relationship with Mrs Camilla Parker Bowles while at the same time being told by the prince to give his depressed wife "instruction", and his position was frankly intolerable.

If the business of a biographer is to distil into a few hundred pages the essence of his subject through the filter of his life and times, then the biography has succeeded. If, further, he can shed light on the times through the lens of one man's life, so much the better.

More difficult to judge are the means taken to achieve it. Clearly in the case of Runcie v Carpenter, Runcie said what Carpenter says he said. The only question is whether he spoke "off the record" and whether that was acknowledged at the time.

"Burbling into it for background," writes the archbishop in the postscript, "I find it reproduced for substance."

Biography is publishing's great growth area. But as academic standards and protocol give way to more populist tastes, the curtain on privacy will inevitably be pushed farther and farther back. It will be a sad day for everyone if vetoes become the norm and "burbling" is no more.

The playwright David Hare called him "a man haunted by his lack of spirituality". For all the book's scurrilous gossip and the C of E equivalent of secrets of the confessional, Lord Runcie is clearly a decent chap, but one who was deceived.

If he was guilty, the sin was hubris - which as a classicist he will know leads inexorably to nemesis.