Lord Stevens' investigation into the car crash which killed Diana, Princess of Wales, and Dodi Fayed will publish its findings at noon on Thursday.
Many do not believe the crash was an accident
His probe has looked into conspiracy theories including claims that the couple were murdered.
A BBC programme claimed DNA tests on the princess's driver proved that he was drunk when the accident happened.
Meanwhile, the US's Central Intelligence Agency has denied bugging the princess on the night she died.
Scotland Yard confirmed Lord Stevens would unveil his findings from his three-year inquiry alongside the Met's Deputy Commissioner Paul Stevenson and senior investigating officer, Det Ch Supt David Douglas.
The princess, 36, and 42-year-old Dodi, were killed along with chauffeur Henri Paul when their Mercedes crashed in the Pont de l'Alma tunnel in Paris in 31 August, 1997.
Dodi's father, Harrods boss Mohamed Al Fayed, is among those who have refused to believe the deaths were an accident.
The couple were chased by paparazzi photographers as they headed to Mr Fayed's apartment, but a subsequent French investigation blamed Mr Paul.
Meanwhile, the BBC's Conspiracy Files programme has claimed the driver was three times over the French drink-driving limit.
There is speculation that the crash report will allege the US's CIA was bugging the princess's telephone conversations in the hours before she died.
But a CIA spokesman said: "The CIA was not bugging Princess Diana's phone conversations on the night she died."
The former Met chief's inquiry, estimated to have cost as much as £4m, is said to bring together some 20,000 documents and 1,500 witness statements.