The Mercedes in which Princess Diana was driven to her death was a dangerous "rebuilt wreck" but concerns about its safety were ignored, French TV claimed last night.
One warning that the car was not fit to be on the road and "didn't hold" if driven at more than 37mph (60km) came only two months before the fatal high-speed accident in Paris on August 31, 1997.
The Mercedes-Benz S280 pool car was provided by the Paris Ritz Hotel, owned by businessman Mohamed Fayed, whose son was Diana's lover Dodi Fayed. The car was owned by Etoile Limousines, which provided chauffeurs and cars to the Ritz, the Daily Mail reports.
Rostain said one of his friends at the Ritz, identified as a driver called Karim, took the Mercedes for a spin earlier in 1997 and warned senior staff about it.
Referring to Frank Klein, the manager of the Ritz at the time, he said: "Two months before the accident, [my friend] ... said to Mr Klein ... that it was necessary to get rid of this wagon. At more than 60 kilometres-an-hour it didn't hold."
Karim said the Mercedes "was not reliable on the road, we were afraid to use it at any speed. I told my manager that we had to sell this vehicle."
Eric Bousquet said he bought the €85,000 car new in September 1994 when he was a "young advertising executive".
Three months later, in January 1995, a prisoner out on remand stole the car, and took it on a joyride in the Paris suburbs.
Travelling at speeds of up to 160km in country lanes, the escapee rolled the two tonne Mercedes around a dozen times, so it ended up on its roof in a field.
The car was considered to be a write-off, and according to Bousquet "the insurance refunded me the price I paid for it, because it was pretty much new, considering it was a destroyed car, non repairable.
"It was considered a dangerous car. I would have liked to take it back, but I was told no, it was not possible," Bouquet told the programme.
The car was condemned as scrap, but finally recovered by a mechanic who repaired it and then resold it to Etoile Limousines.
Neils Siegel, who worked for the company at the time, said he bought the Mercedes for €40,000, but refused to discuss claims that it was not road worthy.
The M6 programme carried out a crash test on the same model of Mercedes, and a technical expert said it "should not have remained on the road", despite being re-built.
It was "not reparable" and "dangerous", the expert added, as he offered a view that was supported by insurance brokers.
Those appearing on the progamme in connection with the Mercedes all said they were particularly astonished that British and French investigators never showed any interest in the car's history.
This is despite the fact that conspiracy theorists suggested it may have been tampered with by those who may have wanted the Princess dead.
Rostain is the co-author of a book called Who Killed Lady Di?, and the tragedy was the subject of a documentary broadcast last night on the French TV channel M6 called Death Of Diana: The Incredible Revelation.
Mohamed Fayed always claimed Diana's death was the result of a bizarre MI6 plot ordered by the Royal Family.
But in 2008 a British jury delivered an inquest verdict of unlawful killing caused by Diana's "grossly negligent" chauffeur Henri Paul, who lost control as he raced at up to 120mph through the Alma Tunnel while drunk and on anti-depressants, and trying to get away from pursuing photographers.
Additional factors were Diana not wearing a seat belt, and the fact that the Mercedes struck the pillar of the Alma Tunnel rather than colliding with something else, the inquest concluded.
Orphelie Meunier, the presenter of the M6 documentary, said: "We are not offering a theory, a new hypothesis, we are really offering verified facts - Diana was not safe in this car."
Meunier said the documentary would help draw a line under the conspiracy theories, adding: "It was nothing but a car accident."
The current owner of the Mercedes is Jean-Francois Musa, 58, the former boss of Etoile Limousines.
Musa, who still lives in Paris, remains locked in a legal battle with Scotland Yard to get the wreckage of the car back.
It was shipped to Britain for police forensics experts to examine in the early 2000s, and is now believed to be in a compound in the UK.
A Scotland Yard investigation into conspiracy theories about Diana's death, led by former Metropolitan Police commissioner Lord Stevens, reported that experts found no problems with the vehicle.
His report, published in 2006, concluded: "Both the French and British examinations of the Mercedes have shown that there were no mechanical issues with the car that could have in any way caused or contributed to the crash."