When Prince William and Prince Harry learned of Princess Diana’s death, it marked one of the worst moments of their lives. At the time, William was 15, while Harry was 12 years old. However, before William was informed of his mother’s death, he had an “awful” feeling.

In the book, “William and Catherine,” Andrew Morton detailed Prince William’s last conversation with Princess Diana and how the teen struggled to sleep through the night as his mother died from her injuries in a car crash.

When Prince Charles told William about his mother’s death, the teen later realized why he had trouble sleeping. “In the morning, as William began to absorb the full import of what had occurred, he said that he thought something awful had happened as he had kept waking up during the night,” Morton wrote.

Earlier this week, Prince William appeared in the “Royal Team Talk” documentary where he reflected on the impact Princess Diana’s death had on his life. “I’ve thought about this a lot […] I think when you are bereaved at a very young age, you feel pain like no other pain,” he said.

The day before William lost his mother, the two spoke over the phone about his concerns over an upcoming photocall.

“While Diana lay on the deck of a luxury yacht under the Mediterranean sun, William was concerned about an edict from Buckingham Palace that he had to attend a photocall to mark his third year at Eton,” Morton wrote.

“It was part of what he considered a Faustian bargain made with the media – he would be left alone to continue his schooling in peace in return for occasional access.”

However, William feared the photocall could go in a different direction because of Prince Harry. “The problem, as he told his mother in that call, was that Harry had been kept back a year at Ludgrove, so the focus of the press was bound to be on his underachievement at school, rather than on William’s steady academic progress,” Morton explained.

“Diana promised to discuss the matter with his father the next day when she arrived home after a night in Paris with Dodi. She never returned.”

Years after her death, Prince William and Prince Harry continue to keep their mother’s memory alive through sentimental tributes and charitable work.

Prince William
Prince William attends the unveiling of The Victoria Cross Commemorative Paving Stones representing each of Birmingham's 1st World War recepients at the Hall of Memory, Centenary Square on Dec. 7, 2015 in Birmingham, England. Getty Images/Richard Stonehouse