On what would have been Princess Diana's 58th birthday, her eldest son surprised well-wishers outside of Kensington Palace, where they were holding a vigil for Diana, who died in 1997.
According to The Daily Mail, royal fans had been stationed outside the palace gates since 5:30 a.m. on Monday, when William shocked them by unceremoniously walking through the gates with a small security detail at 6:45 p.m.
"William told me he knew we'd been coming here for years and thanked us for what we were doing for his mother," John Loughrey, who chatted with the Duke of Cambridge, said. "... He shook my hand three times, he has a really firm shake, and I felt a beautiful feeling go through my body. I think I'm still shaking now. I feel very emotional."
"He said, 'I'm touched by what you do, you've got quite the collection,'" John recalled of William's reaction to his Diana-themed accessories. "I told him that I pray for his mother every Sunday at Westminster Abbey and he seemed really touched."
"She was born with two hearts, one for her and one for us. People must never forget that," John added of Diana. "I have never spoken to William before, only seen him, but he made a beeline for me and he knew who I was. I am so touched. He seemed really moved that we were here."
John, he told the outlet, asked William about the progress with statue of Diana that's set to be placed outside the palace.
"Soon, very soon," William said of when the statue would be unveiled, according to John. "We just want to make sure it is right. It's important to get it right."
Another attendee, Maria Scott, told the Daily Mail that she was there "to honor Diana's legacy."
"We are two generations down now and there are children growing up who don't even know who she is. It's important that we remind them and remember," she said. "None of us could believe it when William suddenly walked down the drive to come and thank us. He really is his mother's son."
William's surprise appearance came just one day before his brother, Prince Harry, paid tribute to his mom in a speech at the Diana Award National Youth Mentoring Summit, an event honoring Diana.
"My mother, Princess Diana, was a role model to so many, without realizing the impact she would have on so many lives," Harry said during his speech. "You don't have to be a princess or a public figure to be a role model. In fact, it's equally valuable if you're not because it's more relatable."
"Being a role model and mentor can help heal the wounds of your own past and create a better future for someone else," he added. "As proven by today's inspirational youth, and many of the stories we've heard this afternoon, the impact of a mentor has the power to make society richer, happier, kinder and more aligned."
Watch the video below for more on how the royal family remembers Diana.