Britain’s Prince William revealed on Thursday that walking behind Queen Elizabeth II’s coffin brought back painful memories after he did the same for his mother Diana when he was a teenager.

William, who now bears the title Prince of Wales, spoke to mourners who, accompanied by his wife Catherine, were leaving flowers at the monarch’s private estate at Sandringham in eastern England.

“Yesterday’s walk was a challenge. He brought back some memories,” William, 40, told a group of well-wishers who had come to see him, footage released by Sky News showed.

William walked alongside his younger brother Prince Harry behind his grandmother’s coffin as it was brought from Buckingham Palace to Westminster on Wednesday.

In 1997, the then 15- and 12-year-old brothers moved the world by walking behind the coffin of their late mother, Diana.

“It’s one of those moments where you’re like, ‘I’ve prepared for this, but I’m not that prepared,'” William told a group of supporters, some of whom were holding flowers.

The royal family traditionally spends Christmas together at Sandringham, with Queen Elizabeth staying into February.

Receptionist Jane Wells, 54, said she told William “how proud his mother would have been of him and he said how hard it was yesterday because it brought back memories of his mother’s funeral.”

Caroline Barwick-Walters, 66, from Wales, said: “He told us how difficult it was yesterday, how it brought back memories of him walking behind his mother’s coffin.”

William and Kate held a tour for almost an hour on Thursday, looking at floral tributes to Queen Elizabeth and shaking hands with people.

King Charles III and members of the royal family will again walk the coffin of the late monarch before and after her funeral on Monday at London’s Westminster Abbey.