Princes William and Harry open up about the last time they spoke to their mother, Princess Diana, in an emotional new doc

Leading up to the 20th anniversary of their mother’s death, Princes William and Harry are remembering Princess Diana in a new documentary. In a clip released this week, they reflect on the last time they spoke to her, and their words are heartbreaking. The documentary, which will air on HBO July 24th at 10 p.m. ET, is called Diana, Our Mother: Her Life and Legacy and features candid, never-before-seen footage of the two men talking about their mother.

They recall the day of Diana’s death specifically: It was August 30th, 1997, and their mother called them from Paris. The two boys were playing with their cousins at the family’s vacation home in Balmoral, Scotland. William, then 15 years old, and Harry, 12 years old at the time, rushed the call so that they could get back to hanging out.

William says in the documentary, “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.”

Harry remembers the call, too. He says, “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.”

But there was no way William and Harry could have known that their mother would die that night in a car crash.

Emotional and raw, the Princess Diana documentary is irresistible TV | @theroyaleditor https://t.co/uC2VDc28td pic.twitter.com/gtkysvHeFC

— Mirror Royal (@MirrorRoyal) July 23, 2017

Harry added:

"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."

The film was directed by Ashley Gething and described by The Washington Post as a “brisk and polite review” of Diana’s life. There are interviews with her sons, close friends, relatives, and employees. It even touches on her marriage to Prince Charles and their separation and divorce. Luckily, it’s not about the conspiracy theories or speculation surrounding her death.

https://www.youtube.com/watch?v=5hkdZSOGK58?feature=oembed

Instead, it gives her sons a chance to reflect on their loss and honor their mother, who is known for being a very down-to-Earth, dedicated woman. She visited AIDS patients in the late ’80s, for example, when other people wouldn’t, and took her sons with her to visit homeless shelters.

Princes William and Prince Harry talk about "best mum in the world" Princess Diana in trailer for new documentary https://t.co/ENyqUePqOQ pic.twitter.com/TJMjsm7WVC

— British GLAMOUR (@GlamourMagUK) July 10, 2017

“She understood there was a real life outside the palace walls. She wanted us to see it from a very young age,” William remembers in the film.

It will definitely be hard to watch, but the documentary seems like a nice way to honor her memory this summer.