An American couple who say they witnessed the car crash that killed Princess Diana, Dodi Fayed, and their chauffeur Henri Paul say that her death was "no accident".
Robin and Jack Firestone say they witnessed the aftermath of the car crash in the Pont de' l'Alma tunnel, Paris, on August 31, 1997, and they reported seeing two dark cars at the scene.
They told The Express that they were stopped by British and French authorities in giving testimonies because the information they offered raised questions about the crash.
Robin Firestone says she saw two dark and mysterious cars that stopped in front of Diana's Mercedes and she believes they were involved in the crash.
The Firestones, along with their 11-year-old son Brandon, had entered the tunnel in Paris just minutes after the crash. They were in the back of a taxi on the way to their hotel.
As their cab pulled up to the destroyed Mercedes S280, Robin, now 63, noticed two "formal" cars in front of Diana's.
"It stands out in my mind so vividly to this day," Robin told the Express.
"I could not understand why they were there. They looked at odds with what had happened. I saw those darks cars, and they must have entered ahead of Diana's.
"They were just awkwardly parked, and I don't recall anyone being in them. The two cars had to be driving ahead of Diana's car. They then buried all reference to them, but they were there."
At the time of the crash, the Firestones did not realise who was in the car.
The mystery vehicles have never been traced.
The Firestones saw no emergency services activity at the scene so they assumed that the accident had happened some time previously, not minutes earlier.
"There was only one police officer stood at the car and a lot of photographers," Jack Firestone told Express.
"He was acting as if it didn't seem like an emergency at all. We thought the survivors had already been taken off to the hospital."
It wasn't until the next morning that they realised the blonde woman they had seen was Princess Diana.
Robin said that when she offered her testimony to authorities she was told "They have enough witnesses. Don't worry about it."
She was dumbfounded. "One of the most famous women in the world is killed and they don't want to speak to witnesses."
Over the next few days, the Firestones say that they repeatedly tried to give a statement to police only to be turned away.
"It was clear the French, and the English didn't want to hear my testimony, and you need to ask why," says Robin.
"I do not think Diana's death was an accident, and the action of the authorities makes me believe that to this day more than ever."
"The whole crash was an establishment thing," says Jack.
"We still live in fear today because of what we saw and what we were told," says Robin. The couple claim her death was not an accident. "I think the crash was a royal thing and other forces were involved," adds Jack. "Something bad could still happen to us. There are enough nuts out there who may try to silence us."
"I hope that one day, as William and Harry grow older that they want to take responsibility to find out what really happened to their mother. If it was my mother I would definitely want to know.
"I hope that some day they will find out the truth."
Prince William has spoken candidly about the death of his mother, describing his bereavement as a "pain like no other pain."
Speaking in a BBC documentary on mental health, William also says that his time working as an air ambulance pilot gave him the impression that death was just "around the door," and the thoughts had become a problem until he spoke with someone.
Prince William and his brother, Prince Harry, have championed the cause of addressing mental health issues, hoping their frank admissions on their own struggles will encourage others in need to seek help.