By Charlotte Wace and Ian Gallagher
Princes William and Harry have bared their souls in the most candid and emotional interview they have ever given about their mother.
Among their revelations, the brothers describe how they are haunted by the final phone call Princess Diana made to them from Paris, hours before her death.
The boys cut the conversation short because they were busy playing with their cousins - something that has caused them heartache to this day. "I have to deal with that for the rest of my life," Harry now says of the fateful decision.
He adds that: "This is the first time the two of us have ever spoken about her as a mother. [It was] arguably probably a little bit too raw until this point. It's still raw."
The result is the most revealing royal interview since 1995, when Diana admitted to having an affair.
William says he thinks of his mother every day and even felt her presence at his wedding. Touchingly, Harry admits that he can "still feel the hugs she used to give us", and misses that embrace.
They paint a portrait of a devoted mother; a caring, passionate woman who had 'the ability to change the mindset of millions'.
Yet they also celebrate her impish streak, with Harry saying "she was a total kid through-and-through" and never happier than when she was with her children driving "through country lanes with the roof down".
Above all, it is their painfully frank recollection of what turned out to be their last conversation with Diana that will hold millions in thrall when their interviews are broadcast on ITV tomorrow night.
The two Princes says they will never escape the deep regret they feel at hastily ending her call from Paris because they were playing in the Scottish Highlands with Peter and Zara Phillips.
At the time - August 30, 1997 - William, then 15, and Harry, 12, were at Balmoral, while Diana was in France with her close friend Dodi Al Fayed, the son of the tycoon who then owned Harrods, Mohamed Al Fayed.
Having not seen each other for nearly a month, Diana and her sons were looking forward to a reunion in London the following day.
William describes the truncated five-minute phone call as his "very last memory" of his mother.
Appearing solemn and occasionally casting his gaze downwards, he says: "I think Harry and I were in a desperate rush to say 'goodbye', 'see you later', and 'we're going to go off'... If I'd known what would happen I wouldn't have been so blasé about it. But that phone call sticks in my mind quite heavily."
Asked if he recalled what his mother said to him, he replies wistfully with a half-smile: "I do, I do," but doesn't elaborate.
When the boys awoke the next day, Prince Charles told them the shattering news of Diana's death in a car accident overnight. She was 36, a year older than William is now.
The phone call is fixed in the mind of Harry, too, and he lays bare his heartache with almost harrowing candour. He recalls William speaking to Diana first then shouting:
"Harry! Harry! Mummy's on the phone." Harry says: "Right my turn, off I go, pick up the phone, and it was her speaking from Paris."
His memories of what came next are fragmentary. "But I do remember regretting... for the rest of my life how short the phone call was.
"And if I'd known that was the last time I'd speak to my mother, the things I would have said to her... Looking back on it now it is incredibly hard. I have to deal with that for the rest of my life. Not knowing that was the last time I was going to speak to my mum, and how differently that conversation would have panned out if I'd had even the slightest inkling that her life was going to be taken that night."
In 1995, Diana plunged the Monarchy into crisis with her Panorama interview in which she revealed she had been unfaithful with Army officer James Hewitt.
With what some regarded as unflinching honesty but others saw as cynicism, the Princess spoke of almost every aspect of her life.
In contrast, the William and Harry interviews, which, like their mother's, were conducted at Kensington Palace, are likely to meet universal approval.
The Princes emerge as assured, confident, well-adjusted adults, who have continued their mother's charity work in a way that would have made her proud.
William appears the most sombre, and speaks in a measured tone. His brother is breezier and, typically, uses humour to deflect often painful subjects.
Both talk about how they struggled to make sense of being robbed of their mother at a crucial stage in their development.
To William, in the throes of adolescence, it was as if an "earthquake had run through the house".
He says: "Your mind is completely split and it took a while for it to sink in. Losing someone so close to you is utterly devastating."
Harry reveals that he has only cried twice since she died - and says he grew up thinking "not having a mother was normal".
Elsewhere in the ITV interview, part of a 90-minute documentary marking the 20th anniversary of Diana's death:
• William says he talks constantly to his own children, George and Charlotte, about "Granny Diana' who, he says, would have 'loved them to bits".
• Harry recalls being puzzled by the "outpouring of love and emotion" from people who had never met her, thinking: "How is it that so many people who have never met this woman, my mother, can be crying and showing more emotion than I was feeling?"
• Harry reveals that he found letters about Diana's work on land mines, dated the day she died, at Kensington Palace only last month.
• William says that he spent years managing his grief by keeping busy.
• Harry recalls her sense of mischief, and says: "Her motto to me was: you can be as naughty as you want, just don't get caught".
The Princes say that, as the anniversary approached, they felt compelled to be more candid in order to celebrate her life and offer "a tribute from her sons".
At a screening of the film for the media, William said: "Harry and I felt that it was an appropriate time to open up a bit more about our mother. We haven't really spoken so publicly about her... and we felt this was the right time to do it. We won't be doing this again."
He added that the film was intended "to remind people of the person she was and what she was like as a mother - the warmth, the humour - which hasn't really come across before".
Diana, Our Mother: Her Life And Legacy, is on Three 8:30pm Tuesday.
Sitting in the sunshine, wrapped in his mother's embrace, Prince Harry beams with blissful delight in one of the last images of mother and son together.
The photograph was taken on holiday and, remarkably, Harry saw it for the first time only recently.
As he explains in tomorrow's ITV film, it was from Princess Diana's personal photo collection, which he had been reluctant to go through. "Part of me never really wanted to look at them and part of me was waiting to find the right time where we could sit down and look at them together," he tells his brother.
William and Harry are filmed poring over the images and the exchanges they provoke - some playful, some touching - demonstrate their close bond.
Opening one of the albums, William highlights the holiday picture of his brother and mother saying to Harry: "This photo here I thought you'd like to see. It's quite a special picture of the two of you, which I thought was quite sweet."
Harry asks: "Where was this, do you remember?" William replies: "This was out on holiday"
Harry adds: "I just remember having the skinniest legs and still do. Skinniest of legs. Chicken legs."
Laughing, William interjects: "You've got some good bushy blond eyebrows going on there as well. And your freckled nose. Your freckles have gone quite a lot now. You used to have such freckles."
Harry says: "No, they come back every now and then," before musing: "Happy memories, good smiley faces... She smothered us with love that's for sure."
Then William notes that "it's really nice looking back at it and reminding yourself... it brought back so many memories".
Many of the pictures they look at in the film, including the holiday snap, have been publicly released to make the 20th anniversary of Diana's death.
One of the most striking is of Diana, in a pink jumper, holding William, while pregnant with Harry, below, which she had captioned "W and Harry".
"Believe it or not, you and I are both in this photograph," says William. "You're in the tummy."
Harry replies: "Oh, nice... You look excited that you've got a brother or sister coming."
William: "I think I was looking forward to beating you up, maybe you're right! I thought that was quite a funny photograph, it was quite sweet."
Harry: "She seems happy there as well."
Talking about a picture of the pair dressed in policemen's helmets, Harry says: "We were dressing up - thinking we were looking really cool."
William replies: "Yeah, that's brilliant. We used to have great fun mucking around, didn't we?"
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