Investigators believe that a Fiat Uno may unwittingly have caused the accident on 31 August which killed Diana, her companion Dodi Fayed, and the driver, Henri Paul.
The possibility that a second car was involved has never been completely excluded and is now being taken more and more seriously by the examining judge and detectives leading the inquiry.
Fragments of yellow plastic from the tail light of a Fiat Uno were found near the crash scene, alongside glass from the front headlight of the Mercedes which was carrying Diana's party. In the last few days, a police laboratory has identified a streak of white paint found on the right wing of the Mercedes as possibly coming from a Fiat Uno (although it could also have come from several other makes of car).
The evidence is sufficiently strong for Judge Herve Stephan to order police to locate every Fiat Uno registered in the Ile de France in the 11 years in which the car was manufactured, from 1983 to 1994.
Investigators believe that the Mercedes, travelling at up to 100mph to escape pursuing press photographers, may have clipped the slower-moving Fiat just before it entered an under-pass beneath the Place de L'Alma in central Paris.
This may explain why the Mercedes span out of control and struck a pillar in the central reservation before rebounding against the opposite wall.
The investigators are said to have rejected all possibility that the low-powered Fiat was connected with the press pack or impeded the Mercedes deliberately (as suggested by some of the wilder conspiracy theories still circulating about the accident).
What remains unclear is how the small car - if it existed - avoided the wildly spinning Mercedes and why the driver fled the scene without stopping.Reuse content