Britain's Prince William and Harry talk about the last phone call they ever had with their mother, Princess Diana, before she died, in a new documentary.
Diana, the first wife of heir to the throne Prince Charles, died in a Paris car crash on August 31, 1997 when William was aged 15 and Harry was 12. She was 36.
Diana, Our Mother: Her Life and Legacy is being released to coincide with the 20th anniversary of her death.
"I think you get the private Diana," Nick Kent, the film's executive producer, told Reuters.
"Nobody has ever told this story from the point of view of the two people who knew her better than anyone else, and loved her the most: her sons."
The princes recall their mother's sense of humour, with Harry describing her as "one of the naughtiest parents".
They also recall the pain of their parents' divorce, and how they dealt with the news of her death and its aftermath.
Earlier this year, William spoke about how the shock of losing his mother still lingered two decades on. Harry said he had sought counselling to help deal with the grief.
While the film addresses such aspect of Diana's life as her charity work involving HIV and landmines, it shies away from more controversial issues, such as extra-marital affairs.
According to the makers, however, the British royals were very open, and did not put any subject off limits. Rather, they wanted to cover new ground and make a different type of film.
"What we had in mind is that in years to come, Princes William and Prince Harry would be happy to show this film to their own children and say this is who your grandmother was", Kent said.
Diana, Our Mother: Her Life and Legacy will be broadcast on British and US television on July 24th.
A number of commemorative events have been planned to mark Diana's death.
William and Harry attended a private service earlier this month to re-dedicate her grave and the brothers have also commissioned a statue to be erected in her honour outside their official London home.
Rarely-seen possessions of Diana, including her music collection and ballet shoes, went on display on Saturday at Buckingham Palace.
An exhibition celebrating Diana's fashion opened in February.
Diana, the first wife of heir to the throne Prince Charles, was killed in a car crash in Paris in August 1997 when William was aged 15 and Harry was 12. She was 36.
