He said instead of helping, some people were taking photographs of Diana on the back seat. "But before I knew it I found myself with a suit on, with a black tie and white shirt, and I was part of it", he recalls.
"William and I know that, we've been told numerous times by people that know that was the case".
The princes previously told the ITV programme Diana, Our Mother of their last phone call with Diana in the hours before her death and their lifelong regret that it was so short.
"She'd had a severe head injury, but she was still very much alive in the back seat".
In the same documentary, Prince Harry praised his father for the handling of their mother's passing. Our grandmother deliberately removed the newspapers, and things like that, so there was nothing in the house at all.
Of the controversial decision by the Queen to keep them at Balmoral away from the press and public in the days immediately after the vehicle crash, the Duke of Cambridge says "our grandmother wanted to protect us".
"The damage for me, being a little boy being eight, nine, 10 and wanting to protect your mother and finding it very hard seeing her upset", he adds. Reported by CNN's award-winning senior worldwide correspondent Clarissa Ward, Diana: Chasing a Fairytale will air Sunday, August 27 at 9pm ET/PT on CNN and CNN global, and Thursday, August 31 at 9pm ET on HLN.
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Yet, a non-violent protester seeking social justice is the greatest threat to the game? "We haven't even gotten that far". He will support whatever decision his teammates make going forward.
He explained in the intimate interview: "When you have something so tragic as the death of your mother when you are fifteen, as many people have experienced and nobody wants to experience, it'll either make or break you".
The Duke of Cambridge said a "pack" would hound and chase his mother, spitting at the royal and calling her names to get a reaction.
At the time of Diana's death, as the world looked for someone to blame, the behaviour of the paparazzi on that night was severely criticised.
What have Princes William and Harry said about the funeral?
Princess Diana was killed in a fatal wreck after her auto, pursued by French photographers, was traveling at high speed through a tunnel in Paris in 1997.
Prince William has opened up about Princess Diana's struggle in dealing with photographers who always followed her around.