Taylor Swift fever has officially taken over the UK as her Eras world tour finally brings her over the pond. A host of A-listers have been spotted in the audience, including Tom Cruise, Nicola Coughlan, Mila Kunis, and Ashton Kutcher.

However, the most famous of all has to be the future King of England – Prince William – who put in lively appearances at Wembley Stadium. Prince William celebrated his 42nd birthday by taking his children, Prince George, 10, and Princess Charlotte, nine, to the first leg of Taylor Swift's Eras tour in London this weekend.

Swift was thrilled with her Royal guests, sharing a selfie of the group, including her boyfriend Travis Kelce and herself, with the caption: "Happy Bday M8! London shows are off to a splendid start."

However, this cheerful message has left some puzzled, questioning if "M8" is some sort of Royal code. One person asked: "What does M8 mean? I thought that it was a motorway?" Another user penned: "guys am i dumb what does M8 mean and who's bday is it?" While a third user questioned: "What does 'M8' mean? I feel like I am the only one who does not know what it means."

Luckily, people were on hand to explain that in reality, there's no hidden meaning - it's simply text slang for the friendly term "mate". Lots of people replied to the confused users, "M8 - mate". Swift and William have been acquainted for years, having shared the stage at a charity event at Kensington Palace in 2013.

This unexpected collaboration saw the then-Duke of Cambridge join the pop star and Jon Bon Jovi in a rendition of Livin' On A Prayer. Reflecting on the moment in a 2021 interview, William admitted: "I can't believe I'm actually telling you this story - I turn up and Jon Bon Jovi and Taylor Swift are at the event, which nearly knocked me off my feet.

"And then, I went inside, met everybody, a lot of handshaking to do those nights, a lot of chatting. I try and be charming and interactive.

"[Taylor] puts her hand on my arm, looks me in the eye and says: 'Come on, William - let's go and sing'." The father-of-three confessed to following her commands "like a puppy" and shared that he felt "cringing" just thinking back on the event. Yet, the 42-year-old evidently has no qualms about ditching his dignity to have a good time now and then.

This was never more apparent than during Taylor Swift's gig in London on Saturday night (22 June), where he was caught on camera wholeheartedly embracing the tunes. At Swift's concert, William was captured by another concert-goer joyously bopping along to Swift's 2014 anthem Shake It Off.

The footage reveals him enthusiastically flailing his arms, sporting an ear-to-ear smile, and thoroughly enjoying the moment. Swifties at the event didn't miss a beat in celebrating the royal's uninhibited show of fandom. One social media maven exclaimed, "Prince William being a 1989 girlie is taking me OUT." Another admirer posted, clearly impressed: "He's a Prince but he's a King for that."

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