King Charles Regrets Making Prince William, Harry Walk Behind Mom Princess Diana's Casket: Royal Biographer

King Charles has deep regrets about making his and Princess Diana's two sons Prince William and Prince Harry walk behind her casket during her funeral, according to a royal biographer.

The new British monarch "deeply regrets" having his children walk at his ex-wife's funeral in 1997 after learning how it affected them. Prince Harry previously said that the thought was "triggering" to him.

"I think it haunts him because it haunts them, and they've spoken about it," American journalist Christopher Andersen told Us Weekly while promoting his new biography "The King: The Life of Charles III." "I've written that I believe it's a form of PTSD."

"[He said] it reminds him of that day when he had to walk behind the coffin, and they were more or less bullied into doing it by the palace — by the men in gray who really run the palace, the people that Diana used to complain about," the writer explained. "[Charles, Earl Spencer], Diana's brother ... has also said that he felt that he was tricked into doing it and regrets it. He said it was like walking through a tunnel of grief."

Millions of people watched Prince Philip, King Charles, Prince William, Prince Harry and Charles Spencer walk behind Princess Diana's coffin during the procession of her funeral. However, it was very upsetting to King Charles and Princess Diana's sons, who were forced to grieve the loss in front of mourners they didn't know.

"I think both William and Harry thought, 'Who are these strangers who never met her?'" Andersen continued. "So they were angry about what had happened. And Charles, I think, understands that to some extent he was responsible for them having to suffer through [that]."

International Business Times could not independently verify Andersen's claims.

Prince William was only 15, and Prince Harry was 12 when their mom passed away in a car crash in Paris.

Prince Harry didn't hide his dismay about the incident.

"My mother had just died, and I had to walk a long way behind her coffin, surrounded by thousands of people watching me while millions more did on television," he told Newsweek in June 2017. "I don't think any child should be asked to do that, under any circumstances. I don't think it would happen today."

On the other hand, Prince William opened up about his experience in HBO's documentary "Diana, Our Mother: Her Life and Legacy" in 2017.

"Slowly, you try to rebuild your life, you try to understand what happened. I kept myself busy, as well, to allow you to get yourself through that initial shock phase. We're talking maybe as much as five to seven years afterward," the Prince of Wales said.

"The King: The Life of Charles III" hits shelves Tuesday.