It’s a day in history that will never be forgotten.
But the young princes didn’t walk alone.
For years, many questioned why Prince Philip would choose to walk behind the coffin, as he was said to have had an “intense dislike” for Diana.
But now, in royal author Ingrid Seward’s latest book My Husband and I: The Inside Story Of The Royal Marriage, the reason behind Prince Philip’s baffling decision has finally been explained.
Originally, Diana’s brother Earl Spencer wanted to be the only person to walk behind Diana’s coffin.
"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 wrote.
"Another of the by-now interminable rows ensued over the telephone, which Spencer ended by hanging up on the prince," she continued.
"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."
But while Earl Spencer and Prince Charles eventually settled their disagreement, Prince William, who was 15 at the time, refused to walk behind his mother's coffin without his grandfather Prince Philip beside him.
"At first William flatly refused. Charles pleaded with him and said that it would be utterly wrong of him not to accompany them," Seward wrote.
Although Prince Philip and Diana's relationship had fallen apart, Prince William and his grandfather were said to be incredibly close.