A French couple testified Monday at a British inquest that they saw an erratically driven white Fiat Uno emerge from a Paris tunnel at about the time Princess Diana's car crashed there 10 years ago.

The car is a missing piece of the puzzle in the crash that killed Diana, her companion Dodi Fayed and driver Henri Paul on Aug. 31, 1997. Police concluded that their Mercedes had collided with a white Fiat Uno, but never found the car and were uncertain whether the collision was a factor in the fatal crash.

Georges and Sabine Dauzonne, testifying by videolink from Paris at a coroner's inquest in London, said they thought the driver of the slow-moving, weaving car was drunk. As they overtook the Fiat, they noticed that the driver was looking intently in his interior and left-side mirrors.

"When we heard of Diana's death, we thought he was most likely looking in his mirrors to see what had happened in the tunnel," Mrs. Dauzonne said.

The couple's Rolls Royce did not travel to the westbound lanes of the tunnel, where Diana's car crashed, but joined the expressway further on, where they encountered the Fiat.

Dauzonne said he was going about 30 kph (20 mph) when he noticed the Fiat, which was traveling even slower. He and his wife both described the car as weaving first to the right toward their approaching car, then to the left, then back to the right.

Richard Keen, a lawyer representing the family of Henri Paul, and Ian Croxford, representing the Ritz Hotel in Paris, which employed Paul, both asked Dauzonne whether he believed the Fiat was deliberately trying to block cars behind it.

"I did not have the impression in this case that he was doing it on purpose, no," Dauzonne said. "He was trying to see what was going on behind him."

Dauzonne and his wife said they did not hear a crash or see anything in the tunnel.

Both said they were certain that the car was a Fiat Uno because Mrs. Dauzonne's mother owned that make of car at the time.

Mohamed al Fayed, who alleges that his son and the princess were the victims of a conspiracy orchestrated by Prince Philip, the husband of Queen Elizabeth II, has claimed that a white Fiat owned by the late photographer James Andanson may have been part of such a plot.

Andanson died in 2000. French police examined his car and concluded it had not been involved in any collision with a Mercedes.

Stephane Darmon, a motorcycle driver for paparazzi photographer Romuald Rat, had chased the couple's Mercedes after it left the Ritz Hotel. He said he saw no other bikes or cars other than the crashed Mercedes when they caught up with it in the tunnel.

"There was nobody in front of me or beside me," said Darmon, who had been working for the Gamma photo agency. Other photographers arrived quickly, "but they were all behind me."

Other witnesses have reported seeing motorcycles close behind or alongside the Mercedes as it entered the tunnel. Darmon said he had fallen far behind the Mercedes, and could not say whether any bikes had been close to it in the seconds before the crash.

When he and Rat entered the tunnel, "there was a lot of smoke and the horn was sounding."

He said Rat pulled open a door of the car, just as the others arrived.

Darmon testified that two or three photographers scurried away when they heard the sirens of the approaching fire brigade.

Earlier in the day, Darmon said he had been among the photographers waiting outside the Ritz Hotel hoping for a shot of Diana and Fayed. Interest was high at the time because of rumors that the couple were about to become engaged.

Darmon said Paul had acted jolly and "playing games" in his encounters with photographers, and gloated over the excitement caused by a dummy departure run by the couple's usual car.

Something in Paul's demeanor reminded Darmon of his alcoholic father, he said.

French and British police concluded that Paul was over the legal limit for alcohol and driving too fast when he crashed in the tunnel. Fayed contends that the blood tests were faked.