It's hard to believe it's been 20 years since Princess Diana died at the age of 36, in a fatal car crash in Paris.
And now, following the release of a collection of private photos belonging to their mother to commemorate the occasion, Prince Harry and Prince William have finally opened up about the last time they spoke to their mother.
In an ITV documentary to mark 20 years since their mother's death – scheduled to air on Monday 24 July – the princes admitted their phone call with their mother was 'desperately rushed'.
Prince Harry, who was 12-years-old when Princess Diana died and has since opened up about the therapy he has received to deal with his grief, said: '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. 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 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,' he added.
Prince William, who along with his brother described their mother as a 'total kid through and through', also remember his last conversation with his mother.
'The very last memory I have is a phone call from Balmoral,' Prince William said.
'At the time, Harry and I were running around, minding our own business, playing with our cousins and having a very good time. Harry and I were in a desperate rush to say 'Good-bye, see you later, can I go off?' If I'd known what was going to happen, I wouldn't have been quite so blasé about it. That phone call sticks in my mind quite heavily,' he added.
During the interview, Harry also admitted he thought growing up without a mother was 'normal' and revealed he has only cried twice since her death.
The brother also described their parent as being the 'best mother ever', who 'brought a breath of fresh air to everything she did'.
'One thing I would love to ask her now, because I genuinely think that she got satisfaction out of dressing myself and William up in the most bizarre outfits, normally matching,' Harry joked.
'It was weird shorts and, you know, little sort of shiny shoes with the old clip on. Looking back at the photos it just makes me laugh – I just think: "How could you do that to us?"
I sure as hell am going to dress my kids up the same way,' he admitted.
Harry - who is currently dating American actress Meghan Markle – also said one of his mother's mottos was: 'You can be as naughty as you want — just don't get caught'.
Imagining what Diana would have been like as a grandmother to Prince George and Princess Charlotte, William joked: 'She'd come in probably at bath time, cause an amazing amount of scene, bubbles everywhere, bath water all over the place, and then leave.'
With the hope their personal story about how they've coped with their mother's death will remind the public of their mother's generosity, kindness and achievements, the Duke of Cambridge also pointed out it would be the first and last time they'd speak so candidly about their family's experience of loss.
'We won't be doing this again – we won't speak as openly or publicly about her again, because we feel hopefully this film will provide the other side from close family friends you might not have heard before, from those who knew her best and from those who want to protect her memory, and want to remind people of the person that she was,' he added.
The documentary 'Diana, Our Mother: Her Life and Legacy' will air on ITV on Monday 24 July at 9pm.