24/08/2017 1:17 AM AEST | Updated 24/08/2017 2:16 AM AEST

Prince Harry Criticises Paparazzi Who Photographed Diana As She Was Dying

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Prince Harry during the marathon. Action Images via Reuters / Matthew Childs Livepic

We will never forget the awful photos of the crumpled car in which Princess Diana met her untimely fate. But for Prince Harry and Prince William, it's the knowledge that paparazzi took photos of their mum as she lay dying in the back seat that will haunt them the rest of their lives.

In a new interview for a BBC documentary airing Sunday called "Diana, 7 days," Harry condemns the photographers who took pictures of his mother rather than help the princess who lay critically injured in the wreckage of the car before she was taken to hospital. She later died of her injuries.

In the interview, the 32-year-old prince explains that he still isn't over how the paparazzi behaved at the time of the crash.

"I think one of the hardest things to come to terms with is the fact that the people that chased her into the tunnel were the same people that were taking photographs of her while she was still dying on the back seat of the car," said Harry.

Harry added that he and the Duke of Cambridge had been told this information about the photographers numerous times by "people that know that was the case."

"She'd had quite a severe head injury but she was very much still alive on the back seat," he said, adding, "and those people that caused the accident, instead of helping, were taking photographs of her dying on the back seat."

"Those photographs" then made their way to news desks in the U.K., he concluded.

Those people that caused the accident, instead of helping, were taking photographs of her dying on the back seat.

The princes have been opening up lately about Diana to mark the 20th anniversary of her death, which falls on August 31.

In a documentary called "Diana, Our Mother: Her Life and Legacy," Will and Harry spoke out about their mum for the first time together, and reminisced on their childhood spent with her.

"She was one of the naughtiest parents," Harry quipped.

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The Prince and Princess of Wales, Prince Harry, and housemaster Dr Andrew Gayley (behind) escort Prince William (2R), second in line to the throne, for his first day of term at the world famous Eton College September 6, 1995. Princess Diana and her millionaire companion Dodi Al Fayed were killed in a car crash August 31 in Paris after being chased by photographers on motorcycles. DIANA

Will agreed, adding that Diana enjoyed having a good time.

"She was very informal and really enjoyed the laughter and the fun," he said. "But she understood that there was a real life outside of palace walls."

Harry also described Diana as the "best mum."

"She was our mum. She still is our mum. And of course, as a son I would say this, she was the best mum in the world. She smothered us with love, that's for sure," he said.

In April, Harry opened up about the mental effects his mother's death had on him, explaining to The Daily Telegraph that he had nearly suffered breakdowns afterwards and had needed counselling in his late 20s.

"My way of dealing with it was sticking my head in the sand, refusing to ever think about my mum, because why would that help?'' he said of his mindset in his teens and 20s.

"All of a sudden, all of this grief that I have never processed started to come to the forefront and I was like, there is actually a lot of stuff here that I need to deal with."

Diana was 36 when she was killed following the car crash in Paris. At the 2008 inquest into her death, it was ruled that the gross negligence of the car's driver, Henri Paul, who was drunk, and the paparazzi were to blame for the crash.

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