Travis Kelce Says Prince Willam Was 'the Coolest Motherf-------' After Meeting Him Backstage at Taylor Swift's London Concert

Travis Kelce is still shocked he met Prince William and his two eldest kids, Princess Charlotte and Prince George , while he was backstage with his girlfriend, Taylor Swift , following the first night of her string of shows in London on Friday, June 21.

“Dude, he was the coolest motherf------,” the football star, 34 told his brother, Jason Kelce , on the Wednesday, June 26, episode of their podcast, "New Heights." “He was so cool!”

“I didn’t realize this because obviously we’re backstage meeting him because he was there with little George and Charlotte, and they were an absolute delight to meet,” Travis continued.

Travis admitted he was nervous about breaking royal protocol upon meeting William, who turned 42 on June 21.

“Wasn’t sure if I was supposed to like bow to them, curtsy, just be an American idiot and shake their hand,” he said.

Jason, 36, added that he and his brother "did get [a] warning" about how to greet the royal family.

“But they said that because we weren’t at like an official royal event, we didn’t need to bow or curtsy . If it would have been like an official meeting of royalty event, then it would have been that. But I did still address him as Your Royal Highness,” Jason said.

As OK! previously reported, the "Cruel Summer" songstress, 34, posted an adorable selfie with William, Charlotte, George and Travis after the concert.

“Happy Bday M8! London shows are off to a splendid start 🇬🇧🇺🇸🤝,” she captioned the sweet selfie via Instagram.

For his part, William wrote, "Thank you @taylorswift for a great evening! #LondonTSTheErastour."

William danced the night away, especially when "Shake It Off" came on , but apparently, it was Charlotte's idea to attend the show as she adores the Grammy winner.

"Princess Charlotte is the huge Taylor Swift fan in the family," a source spilled. "She has wanted to go to the concert for months, but with her mum [ Kate Middleton ] being treated for cancer, this was a really special day to be able to celebrate her Papa's birthday like this."

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"They are really wonderful children. William and Kate have done a fantastic job raising all three of them," the insider said, also referring to 10-year-old George and 6-year-old Prince Louis , who stayed back with Kate Middleton, 42, as she battles cancer . "They understand and appreciate how lucky they are meeting someone like Taylor Swift ."