In a new documentary set to air on Monday, Prince William and Prince Harry explain how the brevity of their final conversation with their mother, Princess Diana, still haunts them.
"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 the documentary, describing their final call with Diana while she was vacationing in France. "But that phone call sticks in my mind, quite heavily."
Harry told filmmakers that the call is something he will regret for the rest of his 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," Harry said.
The ITV documentary "Diana, Our Mother: Her Life and Legacy," which will also air on HBO in the United States, is one of a series of tributes to Diana expected as the 20th anniversary of her death on August, 31, 1997, approaches.
William was only 15 and Harry was 12 at the time of Diana's death. Only in the last year have the brothers spoken openly about the sudden loss of their mother.
In addition, the documentary highlights Diana's charitable works, including her outreach to AIDS victims and her campaign to ban landmines.
It also stresses Diana's fun-loving side, which William and Harry said the public didn't usually get to see.
William said he frequently tells his children about his mother, so Diana can be a presence in their lives.
The Associated Press contributed to this report.