The judge leading the official investigation into the crash has called a "general confrontation" of witnesses and suspects - an event eerily reminiscent of the last chapter of an Agatha Christie novel. The only notable absentee will be the sole survivor of the crash, the bodyguard Trevor Rees-Jones, who has declined to attend.
The participants, behind closed doors in a court-room in the Palais de Justice in Paris, will include Mohamed Al Fayed, father of Diana's companion, Dodi Al Fayed, who also died in the crash. They will also include the nine press photographers, and one press despatch rider, placed under formal examination for their role in the accident.
When first announced two months ago, it seemed the "confrontation" - a common device in French judicial inquiries - would mark the beginning of the end of the nine months' investigation. According to leaks from the inquiry, this may not now be the case.
Interminable technical investigations of the wreckage of the Mercedes are not yet complete; they may not be ready until October, 14 months after the accident. By bringing all the principal participants together - press photographers, police, a dozen eye-witnesses - Judge Herve Stephan hopes to close some of the gaping holes which persist in his re-creation of the events of the night of 30-31 August last year.
How close were the pursuing press motorbikes when the Mercedes carrying Diana's party crashed into the 13th pillar of the underpass? What was actually seen of the white Fiat Uno suspected of having been in a glancing collision with the Mercedes before the accident? How callously did the photographers behave in the minutes after the crash (at least three are known to have taken pictures of the dead and dying victims).
The hearing is not a trial: it will not point the finger of blame. It will force the witnesses and suspects to test their often conflicting accounts, one against the other, face to face. It will not consider the dozens of conspiracy theories about the crash, propagated, amongst others, by Mr Fayed, British tabloids, French scandal magazines, the Internet and Colonel Gaddafi.
Sources close to the inquiry have always insisted that they have discovered no scrap of evidence which suggests that the crash was anything but an accident.
Judicial sources in Paris declined to comment yesterday on the latest revelations by an ITV documentary, and in the Spectator magazine, about the driver of the Mercedes, Henri Paul. Both said that tests on Mr Paul's body after the crash revealed that he was driving with an abnormally high level of monoxide poisoning in his blood, as well as mind-calming drugs and three times the legal limit of alcohol.
Despite the length and intensity of the investigation, it appears that Judge Stephan is not yet able to say precisely why the Mercedes limousine spun out of control soon after midnight on Sunday 31 August. But the facts which have been established mean that a supreme act of will is necessary to sustain a theory of conspiracy, plot and assassination.
It would have been impossible for any would-be assassin or assassins to know the movements of Diana's party that night; the final route of the Mercedes was decided by Dodi and Mr Paul minutes before the crash. In any case, Diana would probably be alive today if she had worn her seatbelt.
The known facts of the night's events are these. The driver, Mr Paul, had taken nearly three times the permitted level of alcohol. He had also taken anti-depressant drugs. He was not qualified as a chauffeur and was not licensed to drive that type of car (an armoured limousine).
The car was travelling at high speed just before the crash, probably at 90 to 100mph.
The party was returning to Dodi's flat just off the Champs-Elysees, closer to the Ritz than the Place de L'Alma where the crash happened. A detour, along the fast roads beside the river Seine, was chosen by Dodi to try to shake off the paparazzi.
The facts which are not clear or disputed are as follows. How close were the pursuing bikes when the accident happened? The photographers say they had been left trailing far behind; some eyewitnesses agree; others say that at least one bike was close to the car. Fragments found at the crash site suggest that the Mercedes may have given a glancing blow to a white Fiat Uno before it crashed. But what happened to the Fiat?
Who could possibly have planned to ram the Mercedes at that place, at that time? With a Fiat Uno?
The most lethal places to drive in Paris are the Boulevard Peripherique and the roads beside the quays of the Seine. The most common contributing causes for accidents were drink, speed and failure to fasten seat-belts. Apart from the identity of the victims, and the pursuing press pack, the night's events fit the classic profile of accidental death on the roads of the French capital.Reuse content