LONDON — The long-awaited report into the death of Princess Diana has systematically demolished every conspiracy theory surrounding the crash, concluding that it was an accident caused by the driver, who was drunk and driving too fast when he lost control of the car.

The result of the two-year “Operation Paget” investigation by the former Metropolitan Police Commissioner, Lord Stevens, which will be published on Thursday, is a devastating rebuff to Mohammed Fayed, whose son Dodi died in the crash.

The 400-page report takes apart Mr. Fayed’s claim that the British secret service murdered the princess because she was pregnant with Dodi’s child. The chauffeur, Henri Paul, while not “blind drunk,” was more than three times over the French legal limit, had traces of tranquilizer drugs in his body, and was driving at up to 100 mph.

Metropolitan Police officers used advanced computer technology to reconstruct the crash scene and examined the Mercedes in painstaking detail. The team took new forensic tests on tiny droplets of the princess’s blood from the back seat of the car, and they were found not to have the hormone levels of a pregnant woman.

The princess’s closest friend, Rosa Monckton, told the inquiry that when they were on holiday together only 10 days before the crash, Diana’s menstrual cycle had started.

Mr. Fayed’s claim that he had been told the princess’s final words by a nurse at La Pitie-Salpetriere hospital where she died is also undermined by the statement to the inquiry from the hospital that the princess never regained consciousness.

Mr. Fayed is expected to challenge the findings, as the only comfort he can draw from the report is that it does not hold his employee, Mr. Paul, solely to blame for the crash in the Pont de l’Alma underpass. While the French investigators made light of the role of the pursuing paparazzi, Lord Stevens maintains that the deadly chase with the photographers was a major contributory factor.

The conclusions will come as no surprise to Prince Charles, but the publication will still be a huge relief to him, Prince William, and Prince Harry, who have been deeply distressed by the repeated public claims of Mr. Fayed that the royal family was behind her death.

The day after the report is published Queen Elizabeth, Prince Philip, Prince Charles, and the Duchess of Cornwall will be at Sandhurst Military Academy for William’s passing out parade. Buckingham Palace officials hope that the ceremony will publicly demonstrate that Diana’s sons are moving on with their lives. Prince Charles and his sons will be briefed on the contents of the report 24 hours before Thursday’s publication.