London UK - Taylor Swift's Friday Eras Tour concert in London's Wembley Stadium was attended by none other than the British royal family, who were out celebrating Prince William's 42nd birthday.

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The first clue should have been when the British Army Corps dropped their Changing of the Guard (Taylor's Version) to herald the Fortnight singer's arrival on the UK leg of her Eras Tour.

Royal reporter Roya Nikkhah shared that Taylor's Friday concert in London was apparently graced by the Prince of Wales and his kids, Prince George (10) and Princess Charlotte (9.)

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The meeting was confirmed by some snaps posted to the Kensington Royal X account showing the Shake It Off singer with the royals, joined by Taylor's boyfriend Travis Kelce.

Will's wife Kate Middleton wasn't seen at the event, which is understandable given her ongoing cancer treatment.

While she briefly returned to public engagements for her father-in-law King Charles' birthday celebration on June 15, Kate is still taking things slow as she continues along her recovery journey.

Prince William's sister-in-law Meghan Markle has reportedly tried to join TSwift's squad in the past to no avail, but William has had his own run-in with the princess of pop.

Back in 2013, he joined Taylor and Jon Bon Jovi on stage for an impromptu performance of Livin' on a Prayer at a Kensington Palace charity event.

The prince described the "off the cuff" moment in an episode of Apple Fitness+'s Time to Walk series.

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"[I was] sat next to Taylor Swift. She [was] on my left. And after Jon does his first song, there's a pause and she turns to me. She puts her hand on my arm, looks me in the eye, and says, 'Come on, William. Let's go and sing,'" he recounted.

"To this day, I still do not know what came over me."

"But, frankly, if Taylor Swift looks you in the eye, touches your arm, and says, 'Come with me…' I got up like a puppy and went, 'Yeah, okay, that seems like a great idea. I'll follow you,'" William said.