Prince William and Harry Used To Write Notes To Princess Diana Saying 'It Will Be OK' As Her Marriage Crumbled

Prince William and Prince Harry spoked on a new documentary that will air this Monday on ITV, about how they felt at the last phone call they had with their mother, and how that call still haunt them today.

In one of the most intimate and warm interviews about the royals memories with Princess Diana, the brothers shared how they coped with her death.

"If I'd known what would happen, I wouldn't have been so blasé about it. But that phone call sticks in my mind quite heavily," William said. He did not elaborate on what was said between him and his mother.

The morning after that call, his father woke them up to tell them her mother had died. Diana died at 36, only on year older than William today.

Harry has struggled for more than 20 years to accept his mother's death. During the documentary, he admitted he will have regrets "for the rest of my life, how short the phone call was. And if I'd known that was the last time I'd speak to my mother, the things I would have said to her. ... Looking back on it now it is incredibly hard."

Paul Barrel, former butler of Princess Diana also spoke and said that Prince William and Harry pushed notes under Princess Diana's door saying 'it will be OK' when her marriage to Charles was falling apart.

He said the boys would sleep in her room during the split."She knew how difficult it was for the boys when she and Charles separated. Diana smothered them in love and they always slept in her room during that time and not the nursery.'

In 2012, the Queen famously banned Burrell from a party for former and current staff at Buckingham Palace making it clear he wasn't welcome anymore. the 59 year-old butler was considered a traitor after the princess felt he cashed in on his time with the royal family in a series of books where he revealed some of her secrets.

The documentary, "Diana, Our Mother: Her Life and Legacy" airs on Monday on ITV. It includes interviews with family friends and Elton John.