Duke of Cambridge Prince William gave royal fans the surprise of a lifetime when he made a random appearance outside of Kensington Palace in honor of Princess Diana‘s 58th birthday on Monday, July 1. While remembering his late mother, the prince stepped outside wearing a casual button-down shirt a par of comfy slacks.

Once outside, he greeted fans one by one and thanked them for keeping his mother’s spirit alive. “William told me he knew we’d been coming here for years and thanked us for what we were doing for his mother,” royal admirer John Loughrey told the Daily Mail. “I’m still shaking now. I feel very emotional.”

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John and other royal fans decorated the Kensington Palace gates with beautiful flowers and photos in honor of the beloved princess who died in 1997 in a tragic car accident.

“We are here to honor Diana’s legacy,” royal admirer Maria Scott admitted. “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.”

Even though Prince Harry wasn’t able to join his brother outside of the palace, he has spoken about keeping his mother’s legacy alive in a previous interview that he did with Good Morning America‘s Robin Roberts.

“We will do whatever we can to make sure she’s never forgotten and carry on all of the special gifts, as such, that she had and that she portrayed while she was alive,” Harry said. “I hope that a lot of my mother’s talents are shown in the work that I do.”

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Not only that, but Prince William has also opened up about missing his mother. “I would like to have had her advice,” he told British GQ in 2017. “I would love her to have met Catherine and to have seen the children grow up. It makes me sad that she won’t, that they will never know her.”

Princess Diana would be so proud of her boys today!