The iconic moment the royal men are captured walking behind Princess Diana's coffin is heartbreaking.

Prince Philip, Prince William, Earl Spencer, Prince Harry and Prince Charles are seen with their heads down at Diana's funeral in September 1997, and the reason they followed her coffin has been revealed.

Royal author Ingrid Seward writes in her latest book, My Husband And I: The Inside Story Of The Royal Marriage, about the tragic weeks following Diana's death, The Sun reports.

In one excerpt, she reveals how the royal family disagreed with Diana's brother Earl Spencer who reportedly believed that he should be the only one to walk behind his sister's coffin.

Advertisement

"In a mark of respect to an ex-wife and a departed mother, Prince Charles wanted to walk behind the cortege with William and Harry beside him," Seward said.

"Another of the by-now interminable rows ensued over the telephone, which Spencer ended by hanging up on the prince ... It was made clear to Spencer that, regardless of whatever private feelings he might harbour, the prince and his sons would walk behind the gun carriage bearing the princess's coffin."

However, Prince William had issues with the arrangement and only agreed to doing it if his grandfather, who he is close to, would walk too.

The funeral of Diana, Princess of Wales, at Westminster Abbey in London. Photo / Getty Images
The funeral of Diana, Princess of Wales, at Westminster Abbey in London. Photo / Getty Images

"At first William flatly refused. Charles pleaded with him and said that it would be utterly wrong of him not to accompany them," Seward said.

"Prince Philip weighed into the argument and eventually William agreed to take part — but only on the condition that his grandfather walked beside him."

According to Seward, Princess Diana did not get along with Prince Philip, but Prince William had already grown close to his grandfather.

"Diana had grown to dislike Prince Philip intensely — and he her — but Prince William was devoted to the old man," Seward wrote.

Diana, Princess of Wales, with her sons Prince William and Prince Harry. Photo / Getty Images
Diana, Princess of Wales, with her sons Prince William and Prince Harry. Photo / Getty Images

"Now, William wanted his grandfather at his side in what was certain to prove the most harrowing public engagement the young man had had to endure."

William later admitted in an 2017 interview that walking behind his mother's coffin was "one of the hardest things" he's ever had to do.