"So Long, London." Hey, Prince William!

On Friday, The Prince of Wales celebrated his 42nd birthday at night one of Taylor Swift's The Eras Tour concert performances at Wembley Stadium in London — and the popstar posted a picture early Saturday morning to prove it.

"Happy Bday M8! London shows are off to a splendid start 🇬🇧🇺🇸🤝 @princeandprincessofwales," Swift wrote on Instagram in a selfie featuring Prince William and his two eldest children, Prince George, 10 and Princess Charlotte, 9. The snap also included her first post with Travis Kelce, the Kansas City Chiefs tight end and three-time Super Bowl champion.

Prince William jumps for joy in birthdayphoto shot by Princess Kate

Swift's selfie also marks the first Instagram photo she has posted with Kelce since the pair were first linked in August of last year. The pair started dating after the NFL star called Swift out on his podcast New Heights after he made an unsuccessful attempt at giving Swift a friendship bracelet with his phone number on it at the second Kansas City show of Swift's Eras Tour.

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Prince William and Princess Kate's official Instagram account @princeandprincessofwales also posted a photo featuring a behind the scenes of the "London Boy" singer's selfie, captioning the post "Thank you @taylorswift for a great evening! #LondonTSTheErastour." That photo featured a quartet of Swift and the three Royal Family members sans Kelce.

In a suite to the right side of the stage, Swifties appeared to capture the Prince of Wales shimmying fervently to the chorus of “Shake It Off" in videos shared by multiple fan accounts.

Earlier in the day to celebrate the future king's birthday, the Buckingham Palace military band performed "Shake It Off," titling it "Changing of the Guard (Taylor's Version)". The Royal Family tweeted out a two-minute video of the band performing the chart-topping tune.

Princess Kate, who was not at the concert, is currently battling cancer but recently returned to public life riding in a carriage with her three children, for Trooping the Colour on June 8 to celebrate her father-in-law King Charles III's birthday. The appearance came five months after she stepped away from public life amid her cancer diagnosis.

Princess Kate posted a birthday shoutout featuring the pair's three kids

That's not the only photo where Prince William received a royal birthday shoutout. The Princess of Wales posted a photo to the pair's official social media accounts featuring Prince William jumping for joy with their three children — Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6 — midair while on a sandy beach.

The cheerful moment was captured by Princess Kate in Norfolk, England, in May, Kensington Palace confirmed to USA TODAY Friday.

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"Happy birthday Papa, we all love you so much! Cx," the royal account captioned the photo.

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Contributing: Naledi Ushe