Princes William and Harry reveal how Diana's death left them 'numb' and speak for the first time about how Charles helped them overcome grief

Princes William and Harry have told how they were left "completely numb" when told the terrible news their mother Diana, Princess of Wales had died in a car crash in Paris.

As the 20th anniversary of her death approaches, Harry has for the first time spoken about how his father for protected him and his older brother, the Duke of Cambridge, after her death in 1997 left the nation in mourning.

Harry said he was in a state of "disbelief" and said he refused to accept his mother's death, while older sibling the Duke of Cambridge felt "completely numb" and asked himself the question "why me?" immediately after learning his mother had died.

The pair also spoke about how their relationship with their father strengthened after her death, as part of a new BBC documentary Diana 7 Days, marking the dramatic week after the princess's tragic death.

Harry, who at the time was holidaying at Balmoral with his brother, father, the Queen and Duke of Edinburgh, said: "One of the hardest things for a parent to have to do is to tell your children that your other parent has died.

"But he was there for us, he was the one out of two left and he tried to do his best and to make sure we were protected and looked after.

"But, you know, he was going through the same grieving process as well," he said in the BBC documentary to be broadcast on Sunday

It comes after the two princes faced some criticism over their own ITV documentary "Diana: Our Mother" in which neither prince even mentioned their father and his role in supporting them.

Harry says his reaction to being told the news was one of ‘disbelief’, and there was ‘no sudden outpouring of grief’.

The documentary is to be screened on Sunday and chronicles the days after the princess' death in 1997, featuring contributions by some of the major figures at the time including former prime minister Tony Blair and other Government figures, senior royal aides, Diana's brother Earl Spencer and her friends.

In an emotional interview, Harry and Prince William also reveal their reactions to being told that Diana, Princess of Wales, had been killed in a car crash in Paris.

William says he was "disorientated, dizzy… and very confused". He adds: ‘I remember just feeling completely numb. And you keep asking yourself “why me?” all the time. “What have I done?”

William added that he was determined his mother's death would not break him. He also criticises the paparazzi for acting 'like a pack of dogs' in their pursuit of Diana before the car crash that killed her.

William said today people would find the treatment of his mother "utterly appalling".

He added: "We'd go looking for her to talk to, play, to do whatever, she'd be crying. And when that was the case it was to do with press.

"She'd had a confrontation with photographers on the way to the gym, on the way outside, just trying to do day to day stuff.

"The damage for me was being a little boy aged eight, nine, 10, whatever it was, wanting to protect your mother and finding it very difficult seeing her very upset.

"About every single time she went out there'd be a pack of people waiting for her.

"And I mean a pack, like a pack of dogs, followed her, chased her, harassed her, called her names, spat at her, tried to get a reaction to get that photograph of her lashing out, get her upset."

The Queen faced criticism from the press and public for not returning from her Scottish estate of Balmoral to London quickly enough to acknowledge the huge outpouring of grief following the fatal car crash, that also claimed the lives of Diana's lover Dodi Fayed and the driver Henri Paul.

William said: "At the time, you know, my grandmother wanted to protect her two grandsons and my father as well.

"Our grandmother deliberately removed the newspapers and things like that, so there was nothing in the house at all, so we didn't know what was going on."

He added: "We had the privacy to mourn and kind of collect our thoughts and to try and just have that space away from everybody."

A sea of floral tributes had been left at the gates of Buckingham Palace and Diana's home Kensington Palace in the days after her death and the documentary charts the growing pressure on the monarchy to make a public appearance.

Harry attempted to explain the situation: "It was a case of how do we let the boys grieve in privacy, but at the same time when is the right time for them to put on their prince hats and carry out duties to mourn not just their mother but the Princess of Wales..."

William sympathised with the dilemma the Queen faced: "I think it was a very hard decision for my grandmother to make, she felt very torn between being the grandmother to William and Harry and her Queen role.

"And I think she, you know again like I said, everyone was surprised and taken aback by the scale of what happened and the nature of how quickly it all happened, plus the fact, you know, she was or had been challenging the Royal Family for many years before hand."

Mr Blair, who had only swept to power in a landslide victory a few months before, told the documentary he was woken on the day Diana died by a policeman at the foot of his bed and described the "shock" at learning the "most famous person in the world" was dead.

Later that day he famously described the royal as the "People's Princess" and in the documentary he attempted to sum up the historical figure.

He said: "Today now 2017, you know we see Prince William, Prince Harry as people, people feel a close connection with. They speak like normal people, they act like normal people, you know, people don't find them hard to relate to.

"It's really important to wind back 20 years and realise, I mean, she was the first member of the Royal Family that people really felt behaved and acted like a normal human being."

Mr Blair revealed in his first conversation with the Queen after Diana's death the monarch was aware of the potential harmful effect events could have on the standing of the Royal Family.

He said: "Princess Diana's relationship that she had with the monarchy and the relationship with Prince Charles, there was going to be a risk that the country's sense of loss turned to a sense of anger and grievance, and then turned against the monarchy.

"So that the first conversation with the Queen was an important conversation, she was obviously very sad about Diana, she was concerned about the monarchy herself because the Queen has a very strong instinct about public opinion and how it plays."

The documentary charts how when the Queen, with the rest of her family, decided to return to London the mood among mourners and the wider country changed.

Mr Blair said: "I think in the course of this week the monarchy, and the Queen in particular, showed that they had that capacity to adapt and adjust.

"Realising what from Diana's life they had to, as it were, keep as part of the monarchy going forward."

At the end of the programme Harry echoes comments made in another interview where he said he wanted to leave the Royal Family.

Speaking about the aftermath of his mother's death he said: "Years after I spent a long time (of) my life with my head buried in the sand, you know, thinking 'I don't want to be Prince Harry, I don't want this responsibility, I don't want this role, look what's happened to my mother, why does this have to happen to me'.

"But now all I want to do is try and fill the holes that my mother has left, that's what it's about for us, is trying to make a difference, and in making a difference making her proud."

Additional reporting by PA