Prince Harry Regrets Last Call with Diana: 'If I'd Known ...'

Prince William and Prince Harry are sharing personal photos and intimate reflections in ITV and HBO's "Our Mother Diana: Her Life and Legacy," People magazine reports, including details of their final call with their beloved mother, the late Princess Diana.

The day Diana died, she called her boys — 15 and 12 — at the Queen's Scottish retreat to chat. The princes recall being eager to play outside with their cousins, and now regret rushing.

In the documentary, Harry says, “And if I'd known that that was the last time I was going to speak to my mother, the things that I would... the things I would have said to her."

Sadly, Harry admitted he has only cried over his mom twice — once at her grave 20 years ago and since then "maybe once... So there's, you know, there's a lot of grief that still needs to be let out."

William told a gathering of reporters, including one from People, the doc is "a tribute from her sons to her."

“We feel hopefully this film will provide the other side from her close family friends that you might not have heard from before," William said, "from those who knew her best, and from those who want to protect her memory and want to remind people of the person that she was: The warmth, the humor, and what she was like as a mother, which probably hasn't come across before in many other pieces from other people.”

William confessed he was "possibly the most nervous" he had ever been while waiting to watch the documentary before the press. Still, he referred to the film as "very important."

Along with being important, the documentary could wind up being singular — William and Harry have vowed not to speak this freely of their mother in this way again.