On the National Police Roll of Honour, which pays tribute to 5,000 officers who have lost their lives while on duty, is the name of Barry Albert Mannakee.

It states simply that he died in a traffic collision in May 1987 while travelling home from work.

The former royal protection officer left a wife, Susan, a self-employed reflexologist, and two teenage daughters, Clare and Michelle.

An inquest two months later decided his death was caused on a rainy evening in an accident between a Suzuki motorbike on which he was riding pillion and a Ford Fiesta driven by 17-year-old beautician Nicola Chopp, who had recently passed her driving test.

There the tragic matter might have rested but for the fact that someone in a very high place was grieving for Mannakee. For the 39-year-old policeman had, until a few months before, been Princess Diana’s bodyguard and, in royal circles, they were thought to be lovers.

Bodyguard Barry Mannakee and Princess Diana were thought to be having an affair

When told of the fatal crash by Prince Charles, she is said to have wept uncontrollably. The Prince informed his wife of the death as they were on their way to the Cannes Film Festival. Diana, then 25, is said to have frozen in horror. She tore at her clothes and scratched at her arms and legs, quite inconsolable.

During the flight to Cannes, she could not stop crying and on arrival, her gown had to be adjusted by her lady-in-waiting and dresser to cover the damage she had inflicted on her own body.

Of course, her torment was not known to the outside world. Details of her close relationship with the 6ft-tall East End ‘Jack the Lad’, whose father was a Ford car worker at Dagenham, emerged only some seven years later.

It followed Diana’s comments on a series of videos, parts of which became public, that she made to her speech coach, Peter Settelen, when she had recently separated from Prince Charles and was emotionally vulnerable.

As well as discussing her sex life and her husband’s relationship with Camilla Parker Bowles, she admitted she fell ‘deeply in love’ with someone very close.

Diana didn’t name Mannakee but referred to him as ‘somebody who worked in this environment’, adding: ‘He was the greatest fellow I have ever had. I was always waiting around trying to see him. Um, I just, you know, wore my heart on my sleeve. I was only happy when he was around.’

Asked by Settelen if he provided ‘the intimacy you weren’t getting’, she replied: ‘Yeah.’ The Princess went on: ‘I was quite happy to give it all up [her royal life], just to go off and live with him. Can you believe it?’ Laughing at the memory, she continued: ‘And he kept saying he thought it was a good idea, too.’

An inquest decided Mannakee's death was caused on a rainy evening in an accident between a Suzuki motorbike on which he was riding pillion and a Ford Fiesta driven by 17-year-old beautician Nicola Chopp, who had recently passed her driving test

Sensationally, the Princess went on to say of his death: ‘I think he was bumped off.’

Of course, there have been conspiracy theories that the car crash in Paris which led to Diana’s own death was staged deliberately because she was with the ‘unsuitable’ Dodi Fayed.

But until the Settelen videotape was shown on American TV in 2004, the idea that Mannakee’s end was anything other than an accident had never been taken seriously. What’s more, Diana dramatically claimed on the tape made in the early Nineties that the death had been deliberately arranged by secret service agents because of their romance.

This weekend, more than 30 years after that road crash in East London, the Princess’s video-taped claims are being broadcast for the first time on British TV, in the Channel 4 documentary Diana: In Her Own Words.

Diana’s friends and her brother, Earl Spencer, have bitterly criticised the programme as ‘intrusive’ and damaging to her two sons.

So, what is the truth about Sergeant Barry Mannakee’s demise? Diana hoped to keep their relationship secret while he was her bodyguard. But Palace staff found out was going on.

Mannakee, who was married, was 37 when he was posted to Kensington Palace as the Princess’s personal protection officer in 1985, a year after the birth of Prince Harry and when Diana and Charles’s marriage was already in difficulty.

The night before Prince Andrew and Sarah Ferguson’s wedding in July 1986, Diana kissed her two sons goodnight and headed towards her drawing room in Kensington Palace.

Waiting there for her was Mannakee. ‘The two were alone together when a senior member of Charles’s staff unexpectedly popped his head around the door,’ a Palace source has since said. ‘He found the Princess and her detective in a compromising situation.’

There were already rumours about the unusual friendship. They had been spotted driving alone on the hills above Balmoral the year before. Mannakee had given her a brown teddy bear which she kept on her bed. No wonder tongues were wagging.

Within hours of the incident on the eve of the Yorks’ wedding, Charles was informed by a courtier of his wife’s suspected dalliance. I’m told that a few days later, the Queen was made aware of the allegation by her deputy private secretary, Diana’s brother-in-law Sir Robert Fellowes.

Not surprisingly, Mannakee was summoned before his superiors and accused of being ‘over-familiar’ with the Princess.

He was sacked from all royal duties and switched to the Diplomatic Protection squad — pushed out of Diana’s life for good. Less than a year later, on a wet Thursday evening of May 14, 1987, he was killed in that accident.

At the time, Diana suspected something was amiss. On the video-tape recorded later by her voice coach, she says of Mannakee: ‘It was all found out and he was chucked out. Then he was killed. I think he was bumped off. But, um, there we are . . . we’ll never know.’

She told close friends of her suspicions, too. At the inquest into her death, Hasnat Khan, the heart surgeon who became Diana’s lover after her marriage ended, revealed: ‘Diana was convinced that Barry Mannakee was murdered in a motorbike accident.

‘She felt it was not normal for a motorbike to have this kind of collision. She was very upset at the way Charles chose to tell her about his death. They were on an official visit and it was impossible for her to show her emotions.’

Also, Ken Wharfe, a later bodyguard to Diana, told the inquest into her death that Mannakee had developed ‘red carpet’ fever by becoming too familiar with Diana.

He said: ‘Other members of the royal household were rather jealous of his relationship with the Princess and below-stairs whispers move at a fairly fast pace. I recall vividly that when Mannakee died, Diana came to me and told me about it, terribly upset.’

When told of the fatal crash by Prince Charles, Diana is said to have wept uncontrollably

And a less reliable custodian of the Princess’s memories, James Hewitt, the Army officer who also became her lover, has added to the conspiracy theories by saying he received anonymous death threats and was told to end their relationship. He claimed that an MI5 officer also visited him and warned he could ‘meet the same end as Barry Mannakee’.

So were Diana’s suspicions simply the fantasy of an increasingly paranoid young woman whose marriage had collapsed and who feared ‘dark’ royal forces were out to get her and anyone associated with her?

Could her beloved bodyguard have been killed on the orders of someone in the Establishment?

Just like the circumstances surrounding Diana’s own death, those concerning Mannakee’s are riddled with allegations of planted evidence, vanished witnesses and mystery vehicles.

Crucially, Nicola Chopp, the novice driver blamed for his death, has told the Mail she suspects evidence was concocted by the police and that she was put under ‘intense pressure’ to plead guilty in court to a charge of driving without care and attention.

Adding to the sense of intrigue, Nicola says an unidentified woman in glasses and driving an estate car was involved, but never traced.

Also, Nicola has letters to her lawyer at the time from a young man called Richard Purnell who witnessed the accident and kindly helped her out of her Ford Fiesta after the crash and walked her to her home, five minutes away.

Richard, too, said he saw the bespectacled female driver in the mystery estate. Yet not only has the woman never come forward, but Mr Purnell — the vital Good Samaritan eye-witness — was surprisingly not summoned to give evidence at the inquest into Mannakee’s death.

Ken Wharfe, a later bodyguard to Diana, told the inquest into her death that Mannakee had developed ‘red carpet’ fever by becoming too familiar with Diana

Later, Mr Purnell became a British Airways flight attendant, but lost his long-term memory after a mugging incident in the Canary Islands. Mr Purnell recovered but, a few years ago, committed suicide.

For her part, Nicola now lives in South Carolina, in America, with her husband. She is still haunted, 30 years on, by the noise of the Suzuki 400cc motorcycle that Mannakee was on as it roared towards her car.

There was then a sickening thud as the officer was catapulted from the pillion through the driver’s side rear window.

Mannakee died instantly, his spine broken in two.

His motorcylist colleague and friend, PC Stephen Peet, was found lying concussed behind Nicola’s car. According to official inquest reports, the bike never collided with her car, but skidded sideways before Mannakee fell off, his body hitting her Fiesta.

It is possible to piece together the events leading to the crash.Nicola had set out from her parents’ home in South Woodford, north-east London, not long after 10pm to collect a friend from the Red House pub in nearby Redbridge. They planned to go to a friend’s home for coffee.

Beginning her journey, Nicola drove into a quiet avenue called Hermitage Walk and approached the junction of Woodford High Road.

A novice driver, she warily waited to see if anything was coming, her Fiesta’s indicator blinking to show she was turning right.

‘I saw an estate car coming towards me from the right (along Woodford High Road),’ she said in an interview at Wanstead police station in the early hours of the following morning, according to transcripts.

‘The car was indicating left and I stopped to see if it slowed down in case it hadn’t cancelled its own indicator. As soon as I saw the car was turning left, I began to move.’

In interviews given to the Mail since, she has insisted that her recollection remains the same.

‘I pulled out when the estate car, driven by a woman in glasses, turned safely into Hermitage Walk beside my Fiesta.

‘As I completed my journey onto the other side of the High Road, I saw a motorcycle, which had been behind the estate car, coming straight at me.

‘I braked and stopped, waiting for what should have been a head-on collision,’ she remembers.

But PC Peet, an experienced motorcyclist, expertly veered to the left so he didn’t hit Nicola’s car. Although Mannakee was killed, PC Peet survived — sustaining chest, head and eye injuries. He spent two days in hospital.

In a statement read out at Princess Diana’s inquest he said he believes it was a freak accident, not ‘deliberately staged to kill Barry Mannakee’.

He added that his injuries meant he did not have total recollection of the accident, but said: ‘Any suggestion that I was involved in a conspiracy to cause the collision is preposterous.’

Certainly, few other people would have known in advance of the bike journey of Peet and Mannakee.

Mannakee would normally have driven home himself in a car. But on the rainy evening, he was offered the lift by bike to get back to his family more quickly.

Were Diana’s suspicions simply the fantasy of an increasingly paranoid young woman whose marriage had collapsed and who feared ‘dark’ royal forces were out to get her and anyone associated with her?

The verdict of accidental death came after police investigators gave evidence blamed the crash on a glare of car lights — thought to have come from the rear or side of the mysterious estate car as it turned into Hermitage Walk — which temporarily blinded Peet.

Mannakee’s widow, Susan, accepted the verdict. In a separate — low-key — magistrates’ court case, Nicola Chopp was fined £85.

And so matters were left . . . until Diana’s sensational video-tape claim that Mannakee had been ‘bumped off’ came to light.

His widow, who remarried, refuses to talk about the accident. But Mannakee’s sister, Patricia Emmins, and her husband, Richard, this week said they believe there are ‘unanswered questions’.

As Richard has explained: ‘First, my brother-in-law has this accident, then Diana dies in a Paris car crash. The girl who, apparently, caused Barry’s death was let off with a small fine even though a policeman was killed.

‘However, trying to get to the truth will probably be impossible. We are up against the Establishment — and they only let you know as much as they want you to know.’

As for Nicola Chopp, she still worries about the inconsistencies in the case.

‘I believe, with conviction, I was not the cause of Barry Mannakee’s death,’ she has told the Mail.

‘Accidents can be arranged and something suspicious happened that night. Words that sounded

like police jargon were inserted into my police interview, such as “offside”, a term that I have never used.’

Aspects of the inquest baffled her, too. ‘A policewoman took the stand and read out a statement she said I had given to her. But she and I have never met. It was completely false.

‘The police told the coroner that they had lost the details of witnesses, apart from a doctor called “John Smith”, whom I cannot remember at the crash scene.’

Nicola is a sensible woman of 47. She has kept all the paperwork, the legal letters and police documents about the crash and, in a series of emails this week to the Mail, confirmed her worries remain.

In view of all the rumours, the Mannakee accident was raised at Diana’s own inquest, and former Met Police Commissioner Lord Stevens’s team investigating the Princess’s death also interviewed Nicola at her American home.

Nicola, in a statement for Diana’s inquest, said: ‘I believe it is possible there was a conspiracy involving the driver of the motorbike and/or the driver of the estate car that turned into Hermitage Walk. I am suspicious about the events of that night and all that has followed.’

Mannakee, who was married, was 37 when he was posted to Kensington Palace as the Princess’s personal protection officer in 1985, a year after the birth of Prince Harry and when Diana and Charles’s marriage was already in difficulty

Of course, over the years, unsubstantiated claims have been made that British intelligence services may have been involved in Diana’s death.

And her butler, Paul Burrell, added to the suspicions by saying that the Queen confided in him shortly after Diana’s death about ‘powers at work in this country’.

Burrell did not ask the Queen to clarify what she meant, but Ian Burnett QC, counsel for the Diana inquest, suggested that possible explanations included the Establishment and the security services.

Now, the broadcast on TV tomorrow of Diana’s blunt comment that she thought her ex-bodyguard and former lover was murdered means that all of those conspiracy theories — and more — are being discussed once more.

What we know for sure is that Nicola Chopp believes secrets are being kept about the death of Barry Mannakee. Certainly, Princess Diana went to her grave convinced that he lost his life because of her.

Diana: In Her Own Words, Channel 4, tomorrow, 8pm.