We just can't stop chasing Diana's ambulance

One or two of the theories that eddy around in the wake of her death really are rather seductive

The Queen herself, apparently, warned Paul Burrell that he should "be careful" because there were "powers at work in this country about which we have no knowledge". But Mr Burrell, faithful servant as he styles himself as being, has decided to ignore that advice, and do battle against the dark forces swirling around us.

First and foremost, he has decided to publish a handwritten letter from Diana, Princess of Wales, given to him 10 months before her death as "insurance". In it she reveals that she suspected some person or organisation of "planning an accident in my car. Brake failure or serious head injury in order to make the path clear for Charles to marry".

My initial thought on reading this revelation was that the poor woman should have listened to her own worries, and got into the habit of wearing a seat belt. The conspiracy theorists rattle on about the stuff that doesn't add up in the accident that killed the Princess, her boyfriend, Dodi Fayed, and their chauffeur, Henri Paul. But the fact remains that their failure to take this simple safety precaution was a major factor in their sustaining of fatal injuries.

The Princess's bodyguard, Trevor Rees-Jones, did have a belt on, and that, to me, explains why he survived. Others, though, are happy to believe that he lived, horribly injured though he was, because he was "in on the plot". Henri Paul, some say, was "in on the plot" as well, a sleeper for MI6 who was found after his death to have had many mysterious bank accounts.

Henri Paul, others suggest, was not "in on the plot" at all. On the contrary, even his blood wasn't "in on the plot". Instead, it was substituted for some other person's blood, packed full of booze, two types of prescription drugs, and carbon monoxide. It was this substitute sample that was analysed by French forensic experts, and not his own - presumably blameless - blood.

Various witnesses say that M. Paul was not drunk when he got into the car at the Ritz that night, that he had no history of the depressive illnesses that the drugs found in his bloodstream are used to treat, and that no record of any prescription for them made out in his name has ever been discovered.

Further, since he died immediately upon impact, there was no way that the huge amount of carbon monoxide in his blood - 20 per cent - could ever have been imbibed without him falling unconscious some time before the crash. The grisly blood-cocktail was introduced covertly so that the finger of blame could be pointed at M. Paul, who was employed by Mohamed Al Fayed, well known to be despised by the British establishment.

In fact, some stories go, the Princess wasn't even the target of the putative assassination. Instead it was Dodi, who was variously picked off either to get at his father or to stop him marrying the Princess, converting her to Islam, getting her in turn to persuade William and Harry to convert to Islam, and creating a constitutional crisis on a scale not seen since Henry VIII converted to cockneyism.

One poor internet conspiracist even asks, in a tone of withering cynicism, whether there really were "religious reasons" why Dodi's body had to be buried so quickly. The answer to this, of course, is: "Yes, you ignorant lump, now be quiet and go away."

He won't, of course. None of them will. Most people love a good conspiracy theory - even the Queen, it appears - and the truth is that one or two of the theories that continue to eddy around in the wake of the Princess's death really are rather seductive in their mad, bad way.

Much is made of the mysterious Fiat Uno, a chunk of which was found smeared on the Mercedes in which the three were killed, while the rest of it has never been recovered. My own feeling is that if a person has a tendency towards hitting and running, the revelation that they've actually killed the world's most famous and adored woman isn't likely to make them any more keen to stand up and be counted.

Much is made too of the testimony of witnesses who say they heard an explosion before the crash, like a gunshot or a bomb, or saw an extremely bright white light, which was apparently deployed to blind M. Paul at the moment of the crash. Still more witnesses contradict other witnesses and say that the car was travelling at no more than 60 miles per hour anyway. None of this can be corroborated though, because as the conspiracy theorists always say: "Why is it that none of the CCTV cameras in the Pont de l'Alma tunnel were switched on?"

The meatiest answer to this question, in case you were wondering, comes from the ex-MI6 agent Richard Tomlinson. His theory is that the Princess was assassinated in a joint undertaking between MI6 and the CIA, using a method they had devised some years ago. He has sworn an affidavit saying that he has seen top secret papers from 1992 which detailed the planned assassination of the former Serb leader Slobodan Milosevic. This wheeze deployed a device activated by remote control that disables the brakes on a car and causes it to crash. How it guarantees that the people in the crashed car are killed, he does not elaborate. (Some theorists, though, are keen to point out that it was nearly two hours before the Princess got to a hospital, and that the hospital she was taken to, La Pitié Salpetriere, was by no means the nearest.)

Mr Tomlinson's theories are exhaustively analysed in a book called Hidden Evidence, the authors of which are certain that they're on to something. So, as a matter of interest, is Prince Michael of Albany, who endorsed the contents of the book. Hidden Evidence, though, isn't entirely convincing. It also alleges, for example, that the BBC announced the crash before it had actually occurred. One can't help wondering if perhaps the poor chaps haven't simply forgotten about the time difference between London and Paris.

One can't help wondering, indeed, if the conspiracists haven't forgotten quite a few other things, like the fact that Dodi and the Princess's plans that night were entirely piecemeal. No one knew much about their plans for the evening, even the paparazzi. By following them, they became the people most instrumental in dictating the pair's decisions. When the Queen talks of "powers at work in this country of which we have no knowledge", my guess is that she has the media, not MI6, in mind.

And the media has managed very well in extricating itself from blame in the death of the Princess. Excoriated in the first few days after the accident for its relentless appetite for pictures of Diana, the media has now become her champion, the mouthpiece which will not allow her to be forgotten, that wants justice for her.

The great hole in the investigation into her death that really exercises the theorists is the fact that there has been no inquest, let alone the public inquiry that so many feel should have been immediately ordered. There probably should be an inquest, even though it will neither satisfy, nor stop, the theorists.

This lack of an inquest has come to be the media's great trump card as well. Every new hint of conspiracy, however opportunistic, is cloaked in the public interest question of the missing inquest, the demand, as the Daily Mirror put it yesterday, that "the British public have an absolute right to know what really happened to the Princess". What really happened was that she died in a car crash, chased by the paparazzi. But we, the ladies and gentlemen of the media, won't stop chasing the ambulance.

d.orr@independent.co.uk