A witness claimed that he saw a blinding flash of light in a Paris road tunnel just before the car crash that killed Princess Diana spent.
Francois Levistre, whose testimony to the British inquest differed at key points from other witnesses, testified that he saw two men on a motorcycle ahead of the princess' car, a "major flash of light," and then a crash.
Afterward, he said, the passenger on the motorcycle looked into the crumpled Mercedes and gave a two-hand gesture to indicate "job done."
The inquest is investigating the deaths of the princess and her boyfriend, Dodi Fayed, on Aug. 31, 1997. Henri Paul, who was driving their Mercedes car, also died in the crash.
Fayed's father, Mohamed al Fayed, has claimed that a blinding flash may have been used by rogue British agents in a murder plot orchestrated by Prince Philip, the husband of Queen Elizabeth II.
Both the French and British police ruled out a conspiracy, concluding that Paul was drunk and driving too fast.
Levistre is not the only witness who claims to have seen a flash in the tunnel but was the first to testify to the inquest.
He said he was driving through the tunnel as the incident unfolded, and then stopped at the end and watched through his rearview mirror.
Other witnesses have told of seeing people running into the tunnel after the crash, and of photographers snapping pictures. Levistre said he saw only two men moving around for as long as five minutes.
Questioned repeatedly about why he had told different stories to French police and an examining magistrate, Levistre said he hadn't read the statements that he later signed.
"You know, people ask questions and you just answer," said Levistre, who testified from Paris via a videolink.
He confirmed that he did not call the police but did contact the Ritz Hotel, controlled by Mohamed al Fayed, and The Sunday Times newspaper in Britain.
Bernard Dertavelle, a lawyer for the Ritz, notified police, who then summoned Levistre, he testified.
Levistre said he saw the Mercedes enter the tunnel and a motorcycle pulling out to overtake it. He said he saw no other vehicles.
The bright flash, he said, was directed at the Mercedes from the back of the motorcycle.
He confirmed that he had served a jail sentence on a weapons charge, and felt he had been harassed by the French media after he and his wife were accused of offering a child to a German industrialist. Levistre said his wife acted as a surrogate mother, which led to an investigation in France but no charges.
"Was your reason for calling the Ritz and The Sunday Times to take revenge on the paparazzi?" asked Ian Burnett, lead lawyer for the inquest.
"Well, you are a great philosopher," Levistre said after a pause.
Then, speaking about questions about his past, he said: "I didn't expect this to be put on the table once again and it is ... a big slap in the face that I receive from you."
In a television interview in 1998, Levistre said he had seen a crowd forming in the tunnel.
"I didn't see that," Levistre said Monday, adding that he had been told about it by other witnesses.
He had told British journalists that he returned to the tunnel days after the crash; Levistre said he had found bits of the Mercedes there, even though police say they had already cleared the site.
"I found some things but it is not worth telling you that I found some things because no one will believe me, no one," he was quoted as saying.
"Tomorrow, people will be saying this man is a pathological liar, if you use this information."
"And what was it that you found that you refused to tell everyone about?" Burnett asked.
"I want to think about that," Levistre said.
"Is that long enough?" Burnett said after pausing a beat. "Can you tell us now?"
"No," Levistre said.
Earlier, three French witnesses said they had seen two cars enter the tunnel at speed, roughly side by side.
Two of them reported hearing two crashes, the second much louder than the first, inside the Pont d'Alma tunnel shortly after midnight.
None of the four recalled seeing bright lights.
David Le Ny; his then-fiancee Marie-Agnes, who is now his wife; and her parents, Jean-Claude and Annick Catheline, said they were walking near the tunnel entrance when they noticed the speeding car approaching.
The Cathelines remembered seeing two large, dark cars nearly side by side; Mrs. Le Ny thought there may have been two cars; but her husband - who told police 10 years ago that he saw two cars - now says he remembers only one.
British police estimated that the car was traveling about 60 mph (100 kph) when it slammed into a pillar.
Jean-Claude Catheline believed the first crash was a collision between the two cars, before they entered the tunnel. His wife thought that incident was inside the tunnel. They agreed that the second crash was much louder.
Lord Justice Scott Baker, who is presiding as coroner, has told jurors that debris found on the road indicated that the Mercedes had collided with a white Fiat Uno before hitting the pillar.
The Fiat has never been traced.