Prince William and Prince Harry tell how they are still haunted by regret over a “desperately rushed” last phone call with their mother, who died 20 years ago this year, in a new documentary, Diana, Our Mother: Her Life and Legacy, to be broadcast on Monday evening. 
 
 William and Harry, who were 15 and 12 when Princess Diana died, say in the new interview to mark 20 years since their mother's death that they were on holiday at the Queen’s house in Balmoral, Scotland, when they were called to the phone. 
 
 “At the time Harry and I were running around minding our own business, you know, playing with our cousins and having a very good time,” William says. 
 
 Prince Harry adds: “As a kid I never enjoyed speaking to my parents on the phone. And we spent far too much time speaking on the phone rather than speaking to each other, because of just the way the situation was. 
 
 “And the phone rang and off he [William] went to go and speak to her for five minutes.” 
 
 William then says: “And I think Harry and I were just in a desperate rush to say goodbye, you know, see you later and we’re going to go off. If I’d known now obviously what was going to happen I wouldn’t have been so blasé about it and everything else. But that phone call sticks in my mind quite, quite heavily.” 
 
 Harry says: “It was her speaking from Paris. I can’t really necessarily remember what I said, but all I do remember is regretting for the rest of my life how short the phone call was. 
 
 “And if I’d known that that was the last time I was going to speak to my mother the things I would have said to her. 
 
 “Looking back on it now, it’s incredibly hard. I have to deal with that for the rest of my life, not knowing that 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.” 
 
 The Princes were taking part in the documentary, due to be broadcast on ITV in the UK and on HBO in the U.S. on Monday, which is full of warm and wonderful insights about Diana as a mother. 
 
 Recalling Diana’s sense of humor, Harry comments: “Our mother was a total kid through and through. 
 
 “All I can hear is her laugh in my head.” 
 
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 He adds: “One of her mottos to me was, 'You can be as naughty as you want, just don’t get caught.' 
 
 “She was one of the naughtiest parents. She would come and watch us play football and smuggle sweets into our socks.” 
 
 William says he keeps the memory of his mother alive for his children by “constantly talking about granny Diana.” 
 
 “She’d be a lovely grandmother, she’d absolutely love it, she’d love the children to bits,” he said. 
 
 There were inevitably somber and shocking moments in the film as well. 
 
 Prince William reveals the depth of his antipathy towards the paparazzi in the program, recalling that photographers once spat at his mother to try to elicit a reaction. 
 
 He says: “If you are the Princess of Wales and you’re a mother, I don’t believe being chased by 30 guys on motorbikes who block your path, who spit at you to get a reaction from you and make a woman cry in public to get a photograph, I don’t believe that is appropriate. 
 
 “I sadly remember most of the time she ever cried about anything was to do with press intrusion. Harry and I, we had to live through that.” ||||| Story highlights Prince William says he was in a hurry to get off the phone to go play 
 
 "I do remember ... regretting for the rest of my life how short the phone call was," Harry says 
 
 (CNN) Prince William and Prince Harry have spoken of their regret at the brevity of their final phone call with their mother, Princess Diana, just hours before her 1997 death in a car crash in Paris. 
 
 In a new documentary set to release on Monday by ITV in Great Britain and HBO in the United States, Prince Harry recalls how quickly he got off the phone with his mother. 
 
 The two brothers were at Balmoral Castle in Scotland when Diana called from Paris. 
 
 "I can't necessarily remember what I said, but all I do remember is regretting for the rest of my life how short the phone call was," Harry told ITV. 
 
 Diana, Princess of Wales, on holiday with Prince Harry. 
 
 "If I'd known that that was the last time I was going to speak to my mother, the things I would have said to her," he said. "Looking back at it now -- it's incredibly hard. I have to deal with that for the rest of my life: not knowing that it was the last time I'd speak to my mum, 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." 
 
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– Hours before her death in a Paris car crash, Princess Diana called her young sons to say hello, interrupting Princes William and Harry from horsing around with their cousins—a call they quickly ended with no inkling her life was about to be cut short. "Harry and I were just in a desperate rush to say goodbye, you know, see you later and we’re going to go off," says William in a new documentary that marks the 20th anniversary of Diana's death. "If I’d known now obviously what was going to happen I wouldn’t have been so blasé about it and everything else. But that phone call sticks in my mind quite, quite heavily." Adds Harry: "I can't necessarily remember what I said, but all I do remember is regretting for the rest of my life how short the phone call was." Other highlights from "Diana, Our Mother: Her Life and Legacy," per CNN and the Daily Beast: Harry: "Our mother was a total kid through and through. All I can hear is her laugh in my head. One of her mottos to me was, 'You can be as naughty as you want, just don’t get caught.' She was one of the naughtiest parents. She would come and watch us play football and smuggle sweets into our socks." William: "There's not many days that go by that I don't think of her. Her 20th anniversary year feels like a good time to ... remember, you know, all the good things about her and hopefully provide maybe a different side to her that others haven't seen before." William on that time mom surprised him with a bunch of supermodels at the house: "Cindy Crawford, Christy Turlington and Naomi Campbell (were) waiting at the top of the stairs. I was probably 12 or 13-year-old boy who had posters of them on his wall. And I went bright red and didn't quite know what to say and sort of fumbled, and I think I pretty much fell down the stairs on the way up." The documentary is set to air on ITV on Monday.