Shortly after 9.30pm on a wet May evening 17 years ago Barry Mannakee accepted a lift to his Essex home on the back of a fellow police officer's motorbike.
Within 45 minutes, Mr Mannakee, an officer in Scotland Yard's diplomatic protection squad, was dead. His spine was broken in two places during a collision with a car turning from a side street in suburban east London.
It appeared to be another grim tragedy on Britain's roads. But within 24 hours the significance of the crash became clear when the Prince of Wales turned to his wife in their limousine and told her that her former bodyguard and apparent lover was dead.
The events of that night, some eight months after Mr Mannakee was abruptly removed from his royal post for "overfamiliar behaviour" with his employer, have long helped perpetuate the florid conspiracy industry that continues to be Diana, Princess of Wales's most enduring legacy.
The relationship between the Princess and the detective has assumed new significance after it emerged that, according to Diana, the couple had contemplated running away together.
In video tapes broadcast this week by the American television network NBC, the Princess said: "I was quite happy to give all this up ... Just to go off and live with him. Can you believe it? And he kept saying he thought it was a good idea."
Sir John Stevens, the outgoing Commissioner of the Metropolitan Police, has ordered a re-investigation of the circumstances of Mr Mannakee's death as part of Operation Paget the inquiry into Diana's own death being conducted in preparation for the British inquest due next year.
In the tapes, the Princess said she believed the man with whom she was "deeply in love" was "bumped off" by the security services.
The interviews, conducted by Diana's voice coach, Peter Settelen, and sold for a rumoured £500,000, were carried out in 1992 at a time when the Princess was acknowledged to be psychologically frail and given to making wild accusations.
But while every detail of the car crash that killed Diana in a Paris underpass in 1997 and the relationships that caused it has been pored over, the accident on 14 May 1987 that claimed Mr Mannakee's life and the events that led to it have not received the same degree of scrutiny.
The detective, who was 14 years older than the Princess, became her bodyguard in 1985, rapidly attaining the status of confidant and becoming subject of a growing infatuation.
On the video, the Princess said: "I just, you know, wore my heart on my sleeve. I was only happy when he was around. I was like a little girl in front of him the whole time, desperate for praise, desperate."
When complaints of an unusually close relationship between the pair, including a sighting of them in an embrace and rumours of long drives around Balmoral, surfaced at Scotland Yard in 1986, senior officers removed Mr Mannakee from Royal duties in Kensington Palace and transferred him to the diplomatic protection squad in central London.
Diana described Mr Mannakee as "the greatest friend I ever had". Ill fate ensured the pair could never meet again.
The 39-year-old, who had two children, had not planned to be riding pillion on a motorbike on the night of his death, accepting a lift from his colleague, PC Steven Peet, so he could get home more quickly.
According to records from the 1987 inquest, Mr Peet's 400cc Suzuki motorbike was travelling along Woodford Road in the outer reaches of north-east London at about 35mph moments before the crash.
As an estate car turned left in front of them, a Ford Fiesta driven by Nicola Chopp, then 17, pulled out from a side road, turning right, across the motorbike's path. The stories of Ms Chopp, who now lives in America, and police investigators differ as to whether the Fiesta had completed its turn before what followed. The motorbike swerved and slid to avoid the car, saving Mr Peet's life. But Mr Mannakee was thrown into the rear window on the driver's side. He was declared dead at Whipps Cross hospital.
The inquest recorded a verdict of accidental death and Ms Chopp was fined £85 for driving without due care and attention. And that is how the matter may have been recorded by history but for the possibly paranoid doubts of a woman caught in an unhappy marriage.
An unknown car with dazzling lights was quoted at the inquest as a contributory factor to the crash but the vehicle has never been traced.
Ms Chopp, who along with Mr Peet has been questioned in recent weeks by the Operation Paget team, claims that her statement was changed by police. She said in October: "I do believe that accidents can be arranged and that something suspicious happened that night."
Scotland Yard insisted yesterday that its re-investigation of Mr Mannakee's death was part of the general remit of Operation Paget. Former colleagues said there were no grounds for suspecting the work dark forces on that night.