Millionaire photographer James Andanson had been threatening to write an explosive book.
But Andanson, who had links with the Secret Service, died mysteriously after meeting author Fredieric Dard to discuss the book that would “blow the lid off a conspiracy”.
He was found in a torched car with two bullet wounds in his head, but the authorities ruled it was suicide.
In a bizarre twist, Frenchman Dard also died within a few weeks of their meeting. Last night top investigative writer John Morgan and friends of Mohamed Al Fayed urged police to reopen the investigation into Andanson’s death in 2000.
Aussie-based Morgan, who has written nine books about Diana’s death, is convinced Andanson “is a vital area” of inquiry for police.
“There is no doubt in my mind that James Andanson was murdered because he was getting ready to spill the beans about the part the security services played in Diana’s murder”
Mr Morgan insisted: “There is no doubt in my mind that James Andanson was murdered because he was getting ready to spill the beans about the part the security services played in her murder. To be blunt, he was silenced.”
A close friend of Mr Al Fayed, 84, whose son Dodi died with Diana in the car crash in a Paris tunnel in 1997, added: “We have always believed this man was part of the team that was behind the assassination, and he was killed to shut him up.”
Witnesses said they saw a white Fiat Uno speed out of the tunnel seconds after the crash.
Andanson, who was 54, drove a distinctive white Uno and had trailed Diana and Dodi around France in the final two weeks of his life.
Before his death he boasted that he was the driver of a Fiat that hit the back of Diana’s Mercedes.
Scotland Yard is already taking a fresh look at claims by an ex-SAS sniper that Diana was murdered.