MIAMI (CBSMiami) -- Twenty years after Princess Diana's death, we are hearing for the first time about the last time she spoke to her sons.
In a new documentary debuting Monday night on HBO, Prince William and Prince Harry share their memories. They also reveal regrets over a phone call with Diana that they had no idea would be their last.
Two decades after Princess Diana's sudden and shocking death, her royal sons reminisce about life with their famous mother.
"Probably a little bit too raw up until this point. It's still raw," said Prince Harry.
She may have been the most photographed woman in the world but at home, she was just mum.
"She was one of the naughtiest parents. She would come and watch us play football and, you know, smuggle sweets into our socks," said Prince Harry.
They remember too how she loved to dress them up in silly costumes and to snap family pictures.
"We felt, you know, incredibly loved, Harry and I, and I'm very grateful that that love still - still feels there," said Prince William.
The last time the princes spoke to their mother she was in Paris, hours before she died. They were far away in Scotland with their grandmother – the queen - and in a hurry to go out to play.
"Harry and I were in a desperate rush to say goodbye," Prince William said. "If I'd known now what was going to happen I wouldn't have been so blasé."
Harry, who was then 12-years-old, said "how differently the conversation would have panned out" if he'd had "the slightest inkling" it was to be their last.
Now 35-years-old, William is making sure that Lady Diana is also recognized as granny di by his own two children.
"I - I do regularly putting George or Charlotte to bed, talk about her and just try and remind them that there are two grandmothers, there were two grandmothers - in their lives," said Prince William.
The princes hope to remind a new generation that their mother was more than a glamorous cover girl. She was a trailblazing celebrity activist.
"People now understand the pioneering work she did for things like HIV and AIDS, for homelessness, for the landmine campaign," said Royal Correspondent Roya Nikkah.
The boys who knew her best have now followed her lead and become public champions for the vulnerable like people with mental health problems or injured service men - a cause Prince Harry spoke to CBS This Morning's Norah O'Donnell about last year.
"I hope she'd be incredibly proud and looking down and thinking what we have achieved,"said Prince Harry during the interview with O'Donnell.
It's been clear for some time the princes admire and respect their mother's activism but we're now learning how much they adored her sheer playfulness.
The HBO documentary film 'Diana, Our Mother: Her Life and Legacy debuts Monday night on HBO.
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