Diana predicted her death in a car crash. Paranoia or a plot?

For the conspiracy theorists who have spent six years pondering the significance of the missing white Fiat and the behaviour of the pursuing paparazzi pack, it was manna from a news stand - nine pages of newsprint detailing how Diana, Princess of Wales, believed she would be murdered in a staged car crash.

The latest addition to the catalogue of allegations over the death of Diana in a Paris underpass on 31 August 1997 came in the form of a letter apparently written by the Princess to her butler and confidant, Paul Burrell, 10 months before she died.

Scrawled on red-fringed note paper bearing her insignia of a letter 'D' topped with a crown, Diana claimed that there was a plot to create a road accident through brake failure which would leave her with a "serious head injury" and clear the way for Prince Charles to remarry.

St James's Palace was determined yesterday to do nothing to fan the flames of publicity. A spokeswoman said: "We are not making any comment. There is nothing to say."

The claim, made by Mr Burrell in a book about his life with the Princess which is due to be published next week, was made in the Daily Mirror after it paid a six-figure sum for the newspaper rights to the work, written after the royal manservant's acquittal in January on charges of stealing his former employer's possessions. Mr Burrell was paid an estimated £500,000 advance for the book, entitled A Royal Duty.

Penguin Books, which is publishing the book under its Michael Joseph imprint, has ordered an initial run of 100,000. Trinity Mirror, publisher of the Daily Mirror, refused to comment on reports that it had printed an extra 300,000 copies of the newspaper, the front page of which was headlined: "Diana letter sensation ... Revealed: note that will stun world".

The letter, which Mr Burrell claims was written in October 1996 on one of Diana's "down days" after her divorce from Prince Charles, was allegedly given to the butler as an insurance policy by a princess worried that she was under surveillance by the "anti-Diana brigade".

Mr Burrell said the Princess handed him the letter in an envelope bearing his name, saying: "I'm going to date this and I want you to keep it ... just in case."

The letter, which reveals the fragility of the Princess's state of mind as she talks of being "battered, bruised and abused mentally" over 15 years of public life, contains the name of individual claimed by the Princess to be behind the plot. This has been withheld by the publishers. Diana wrote: "This particular phase in my life is the most dangerous. [Name blanked out] is planning 'an accident' in my car, brake failure and serious head injury to make the path clear for Charles to marry."

Both Penguin and the Daily Mirror said the name had been omitted for legal reasons, namely concern at possible libel proceedings if the individual's identity were to be disclosed. A source said: "There are no active proceedings but this is a preventative measure."

Even without the identity of the individual, the disclosure of the letter will fuel the lucrative output of books, magazine articles and documentaries based on claims rejecting the findings of the French investigation into the crash at the Pont d'Alma tunnel. A French judge found in 1999 that Diana's death was an accident caused by the effect of drink and prescription drugs on the driver of the Mercedes S280, Henri Paul, as he reached speeds of 80mph in a dash from the Ritz Hotel in Paris.

Mr Burrell, who was cleared of theft charges at the Old Bailey after the intervention of the Queen, denied that he had failed to declare the existence of the letter to maximise the impact of his memoirs.

The former butler said he had been spurred to publish because of the failure to hold an inquest in Britain into Diana's death. The Surrey coroner, Michael Burgess, announced in August that an inquest would be held but no date has been set.

Mr Burrell, who Diana famously called her "rock", said: "I decided to write this book because I firmly believe that someone has to stand in the Princess's corner and fight for her now that she cannot do so herself. I will always remain true to my duty."

As internet chatrooms specialising in conspiracy theories yesterday filled with opinions on the significance of the letter, Mohamed Al Fayed, the Harrods owner, whose son Dodi was also killed in the crash, criticised Mr Burrell for not disclosing the letter earlier. Mr Fayed said: "It is extraordinary that Paul Burrell did not volunteer this evidence in time for the French investigation into the crash. But it is now vital that he be called to give evidence in an independent public inquiry.

"It is his civic duty now to tell all that he knows about the involvement of others, including the security services, in this conspiracy."

COVER-UP CLAIMS

The missing Fiat

Chips of paint from a white Fiat Uno were found in the wreckage. Some witnesses said they saw a Uno swerve in front of the Mercedes, causing it to crash. The car contained Mossad agents determined to stop the Princess marrying an Arab and popularising the Palestinian cause.

Henri Paul was an assassin

The Princess was killed by British security services to stop her marrying Dodi and producing Muslim children. A disaffected British agent said Henri Paul, the Mercedes driver, had worked for MI6 and the crash resembled an MI6 plan for assassinations.

The haste of a son scorned

Dodi had proposed to the Princess on the night of the crash but was turned down by a laughing Diana. In his anxiety to leave the Ritz, Dodi told Paul to drive away at top speed from the pursuing paparazzi.

Military laser torch

Paul was dazzled or blinded by a bright light as he entered the underpass: this was an anti-personnel laser used to disable him.

The magic blood test

Two blood tests showing Paul over the drink-drive limit were done on samples from another body.