Prince Harry believed Princess Diana had faked her death to escape scrutiny.
The Duke of Sussex was just 12 years old when his mother died in a car crash in Paris and when the tragic news was broken to him, he was convinced the princess had played a "trick" on the world and the accident was a "diversion" for her to run away and go into hiding.
He said: “With nothing to do but roam the castle and talk to myself, a suspicion took hold, which then became a firm belief. This was all a trick.
“And for once the trick wasn’t being played by the people around me, or the press, but by Mummy. Her life’s been miserable, she’s been hounded, harassed, lied about, lied to. So she’s staged an accident as a diversion and run away.”
After the princess' death, "matrons" at Harry's school asked him to write a "final" letter to his mother, but he still believed she was still alive.
He wrote in his new memoir 'Spare': “I have a vague memory of wanting to protest that she was still alive, and yet not doing so, for fear they’d think I was mad.”
Years later, Harry asked his press secretary to review secret police files on the crash, which also killed Diana's boyfriend, Dodi Fayed, and chauffeur Henri Paul, and was horrified to realise paparazzi were on the scene.
He wrote: “There were lights around her, auras, almost halos. As I realised their true origin, my stomach clenched. Flashes. They were [paparazzi photo] flashes.
“I hadn’t been aware, before this moment, that the last thing Mummy saw on this earth was a flashbulb.”
During the Rugby World Cup in 2007, Harry and his brother Prince William drove through the tunnel where the crash had taken place, and afterwards they discussed the inquest into Diana's death, which they branded a "joke" and an "insult".
He wrote: “Afterwards, we talked about the crash, for the first time ever. We talked about the recent inquest. A joke, we both agreed. The final written report was an insult. Fanciful, riddled with basic factual errors and gaping logical holes. It raised more questions than it answered.”
The pair decided to call for the inquiry to be reopened but "were talked out of it by the powers that be.”
Elsewhere, the 38-year-old prince spoke of his regret that he "rushed" Diana off the phone in their last conversation because he was busy playing with his cousins.
He wrote: “I wished I’d searched for the words to describe how much I loved her. I didn’t know that search would take decades."