Prince William and Harry reveal the final time they spoke to their mother Princess Diana

PRINCESS Diana’s sons have revealed they still feel immense guilt over the way they spoke to their mum hours before she died.

ON THE night of August 30, 1997, a then-15-year-old Prince William and 12-year-old Prince Harry received a phone call from their mother Princess Diana.

But the two young boys were with their cousins in Balmoral and instead of speaking to their mother at length, they rushed the call so they could continue playing.

A few hours later, Princess Diana died in a car accident in the Pont de l’Alma road tunnel in Paris.

Prince William and Harry walk behind Princess Diana’s coffin with her brother Earl Spencer. Picture: Jeff Mitchell

Now, coming up to the 20th anniversary of her death, her two boys have spoken about the crushing guilt they still feel over rushing the call — not realising it would be the final time they’d speak to their mum.

In a brand-new documentary called Diana, Our Mother: Her Life and Legacy, due to air on Seven’s Sunday Night next week, Prince William said it’s still stuck in his mind.

“Harry and I were in a desperate rush to say goodbye, you know, ‘see you later’. 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 heavily,” Prince William said.

And Prince Harry said he struggles to even remember what the call was about.

“It was her speaking from Paris. I can’t really necessarily remember what I said, but all I do remember is probably regretting for the rest of my life how short the phone call was,” he said.

“Looking back on it now it’s incredibly hard. I’ll have to sort of deal with that for the rest of my life. Not knowing that was the last time I was going to speak to my mum, how differently that conversation would have panned out if I’d had even the slightest inkling her life was going to be taken that night.”

Princess Diana with her two boys Harry and William. Picture: Tim Graham

The now 32-year-old prince also revealed that, in the 20 years since his Diana’s death, he has only cried twice — once when she was buried at her family’s Althorp Estate and on one other occasion.

“There’s a lot of grief that still needs to be let out,” he said.

“It has been hard and it will continue to be hard. There’s not a day William and I don’t wish that she was still around, and we wonder what kind of mother she would be now, and what kind of a public role she would have, and what a difference she would be making,” he added.

Prince William and Harry recall fond memories of their mum.

While the two royals have become increasingly open about discussing their grief around the loss of their mother, Prince William said their candid chats aren’t going to become a regular thing.

“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,” the prince said.

Prince Harry especially has become more and more open about the grief he felt after the loss of his mother — including the impact it had on his mental health.

In April, the young Prince sat down with The Telegraphfor a mental-themed podcast revealing that the emotional fallout from trying to run from his grief plunged his life into “total chaos”.

“I’ve spent most of my life saying ‘I’m fine’ ...‘Fine’ is so much better than having to go into the details,” he told interviewer Bryony Gordon.

Prince Harry’s life descended into total chaos after he came to terms with losing his mum. Picture: AFP/Kensington Palace

“If anybody looked at my life, if you look back to the fact I lost my mum at the age of 12 on a public platform ... And everything else that happens with this role and the pressures that come with it. Then going to Afghanistan ... Anybody would look at that and go, ‘OK, there must be something wrong with you. You can’t be totally normal (after that)’,” he said.

Harry served two tours of Afghanistan before leaving the military in 2015.

It wasn’t until Prince William sat his brother down — after Prince Harry’s ‘wild child’ years had him become regular tabloid fodder — that the young royal decided to get help.

“My brother was a huge blessing. He kept saying ‘This is not right, this is not normal — you need to talk about stuff. It’s not normal to think that nothing’s affected you’.

“It was 20 years of not thinking about it, then two years of total chaos. I didn’t know what was wrong with me.”

Prince Harry and William and the Duchess of Cambridge have since supported the campaign Heads Together which encourages young people to talk openly about their mental health issues.

Prince William, Catherine and Harry support Heads Together. Picture: Chris Jackson

Prince William has blasted the royal tradition of keeping a “stiff upper lip” ever since he had to persuade his brother to get help.

“There may be a time and a place for the ‘stiff upper lip’ but not at the expense of your health,” William said.

And in an interview with CALMzine back in April, William said seeing his younger brother struggling had a huge impact on the way he and Catherine are going to raise their children Prince George and Princess Charlotte — to be more relaxed about talking of their emotions.

“Catherine and I are clear we want both George and Charlotte to grow up feeling able to talk about their emotions and feelings,” he said.

Prince William and Catherine, Duchess of Cambridge are raising their children differently. Picture: Patrick Stollarz

The 90-minute documentary features the two royals speaking about the final phone call with their mother and was made in conjunction with the palace.

It also includes individual contributions from the Princess’ family and friends, several of whom have never spoken before.

They include Sir Elton John, Rihanna, The Rt. Hon. The Earl Spencer (Diana’s brother), Harry Herbert, Lady Carolyn Warren, William van Straubenzee, Gerard McGrath, Jayne Fincher (Royal Photographer), Anna Harvey (personal stylist), Lord Victor Adebowale and Graham Dillamore, (Gardens Manager, Kensington Palace).

Diana, Our Mother: Her Life and Legacy will air on Seven’s Sunday Night next Sunday on July 30 at 7pm.