Princes William and Harry speak about 'complete numbness and disbelief' at Princess Diana's death

'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'

The Princes spoke about the day they found out their mother had died (AFP/Getty)

Prince William has spoken of feeling “completely numb” at the news of his mother’s death in a landmark documentary marking the 20th anniversary of the death of Diana, the Princess of Wales.

His younger brother, Prince Harry, said he had been left in a state of "disbelief".

The BBC programme appears to confirm their father and heir to the throne, Prince Charles, broke the news to his sons.

Harry also paid tribute to Charles, saying how he was "there for us".

The Prince, who at the time was holidaying at Balmoral with his older 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.

"How you deal with that I don't know but, you know, 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."

The documentary, Diana, 7 Days, is screened on Sunday and chronicles the days after the princess' death in 1997. It will feature 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.

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."

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.

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."

Press Association