He was one of Princess Diana's closest confidantes, and by her side during the breakdown of her marriage. Ken Warfe tells Nick Morrison why he doesn't feel guilty about spilling the beans on the Princess of Wales.

KEN Wharfe remembers the moment when Princess Diana realised her marriage was effectively over. It was Annabel Goldsmith's birthday party, and the heir to the throne and Camilla Parker Bowles were found in the basement, having sneaked away to be alone. After all the previous humiliations and betrayals, it was this which pushed the Princess of Wales over the edge.

"She told me that was the turning point, that really prompted proceedings for separation and divorce," he says. "I personally believe that the Princess gave it more time than she should have done and she should have realised it was irretrievable earlier, but I defy any woman to live with that."

As Diana's protection officer for seven years during the most turbulent period of her life, Wharfe was an insider to the most publicised break-up in history, aware of all the affairs, the bitterness, the accusations, the smear campaigns.

His decision to write an account of his experiences - newly-released on CD - attracted predictable outrage at yet another royal retainer cashing in, and a former policeman betraying his profession. Princes William and Harry were said to be "incandescent" with rage, and Wharfe himself became the target of a smear campaign, alleging he was a fantasist.

But Wharfe is unrepentant. He decided to write his book, he says, to set the record straight. More particularly, the accusation that Diana was mad, and that she imagined the affair between her husband and Camilla Parker Bowles long before it was reality.

"At a point where her marriage was not reconcilable, Camilla Parker Bowles was very much on the scene, contrary to the spin machine saying it was all a figment of Diana's imagination. It was against that background that I decided to report the facts as they happened.

'All I have done is put the misinformation right. I don't believe William and Harry were incandescent with rage, because if they were to read it they would identify with every single word. I was not concerned because I knew exactly how the princes would react," he says.

Of all Diana's former circle who have chosen to spill the beans, the most high-profile, and most financially rewarded, is Paul Burrell, the former butler who's making a good living out of being Diana's "rock", but Wharfe is dismissive of his claims to be the Princess's most trusted confidante.

"I knew Paul Burrell pretty well and it would be very easy for me to sit and criticise him. I know a lot about Paul Burrell," which sounds rather ominous. "Paul Burrell was certainly not instrumental in her life; he was a bit of a fantasist, and really sought the celebrity status.

"I was often called the rock, the chef was the rock, the butler was the rock. It was a phrase Diana would use almost on a weekly basis to whoever was flavour of the week. It is laughable to think back to the number of occasions when I was the rock one week and the next week was reduced to dust. It took a long time to get back to being in favour."

In line with this, there were mood swings, but he says the advantage of working for Diana was that she was transparent - you always knew where you stood with Diana, even if it was in the doghouse.

"Diana was totally honest, in the sense that you knew exactly what was happening. And with her there were no barriers. With the Queen, there was this royal screen that shuts down and makes them less approachable, but Diana was the complete opposite, everyone was treated with the same status."

It was this informality which helped make Diana such a success with the public, to the obvious irritation of her increasingly estranged husband. But as well as this familiarity and the giggling laugh, Wharfe also experienced the downside, when Diana was in despair at the state of her marriage.

On one occasion, the Wales's were on holiday on a yacht, when Charles spent most of the time phoning his mistress. This was one of many unpleasant episodes.

"It was very difficult for her to put on this face of respectability. I found her in a lifeboat completely pissed off. I said, 'You have got to put on a brave face.' It wasn't my role to speak to her, but in the absence of anybody else, someone had to say something.

"The Princess found it very difficult to accept that her husband was having a relationship, and people were saying she was mad and obsessed with the notion that he was having an affair - but she was right," he says.

Diana's bulimia and suicide bid have also been cited as evidence of her mental instability, but Wharfe says both have been overplayed, and claims her tumble down the stairs was more a cry for help than a serious attempt to kill herself.

Fairly early on in his service for Diana, Wharfe was made aware of her affairs, firstly with James Hewitt and then with Oliver Hoare. In her defence, he says she only started having affairs when she thought there was little chance of saving the marriage.

It's clear that Wharfe's sympathies lie very much with Diana - although he says both parties were ultimately responsible for the marriage breakdown - and this explains why he has been vilified by those on the other side of a bitter divide.

But he says he never counted the Princess as a friend, despite the late-night conversations, when she would come into the kitchen and talk for hours over a cup of tea.

"I was not a personal friend; I had that professional distance. It would have been easy to get sucked in, and there is a disease which affects people in Buckingham Palace, called Red Carpet Fever, for which there is no known antidote. That is where Paul Burrell went wrong, and believed he was almost as royal as the person he was working for.

"It was very informal, very un-royal, and emotionally it was quite draining, but it was an incredibly fun time, a privileged time, and it was a wonderful experience. For me, the Princess was an incredibly talented and wonderful boss to work for and we were all privileged to have somebody like her. If it were not for the royal duty, I think somebody like that could have become a good friend."

He was in the country, away from any phones, when he heard Diana had died. He had stopped working for her more than three years earlier, but was stunned when the news came through on his pager.

"I was shaken. I couldn't believe she had died in a road accident, I thought there had to be a reason," he says.

But when the truth sank in, that Diana was as mortal as the rest of us, he laid the blame largely at the door of the security provided by Mohammed Al Fayed, whose subsequent conspiracy theories Wharfe sees as little more than an attempt to attract attention away from his own role.

"Scotland Yard had protected her for 15 years and she survived. She was with Fayed for six weeks and she is dead. This was an accident caused by a man having too much to drink, and Fayed doesn't want to say he employed the wrong type of security.

"All these fantasies of Fayed's are part of this huge box of speculation but there is no evidence. It was a simple tragic accident, that could and should have been avoided. She was not a friend but I knew her incredibly well. It was a terrible loss," he says.

Diana: Closely Guarded Secret, written and read by Ken Wharfe (Right Recordings, £10.99).