LONDON — It was a typical phone call between two boys and their mother, who was on vacation in France. It was brief – the boys wanted to get back to playing with their cousins, not spend time on the phone chatting.

The brevity of that call on Aug. 31, 1997, haunts Prince William and Prince Harry to this day – for their mother, Princess Diana, would die in a car crash that night.

“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 blase about it and everything else,” William says in a new documentary. “But that phone call sticks in my mind, quite heavily.”

Harry tells the filmmakers the final chat is something he will regret until the end of his days.

The ITV documentary “Diana, Our Mother: Her Life and Legacy” is airing Monday on HBO and on British TV. Excerpts from the film, and new family photographs, were released Sunday.

It is only in the last year that William and Harry have spoken openly about their feelings about the sudden loss of their mother. William – second-in-line for the British throne after his father Prince Charles – was 15 at the time and Harry was 12.

– From news service reports