Taylor Swift made a surprise appearance at Haimâ€™s sold-out concert in Londonâ€™s O2 Arena on Thursday (21 July).
The American rock band comprising sisters Alana, Este and Danielle Haim were midway through performing their hit â€œGasolineâ€ when they stopped suddenly.
Introducing Swift, 32, Alana said: â€œWait, you guys. Weâ€™re in London, we canâ€™t play London without bringing out a special guest.
â€œBecause not only is this person that Iâ€™m about to bring out the most incredible singer, songwriter, producer, f***** amazing person all around, sheâ€™s one of our close friends,â€ she continued, as Swift walked onstage to thunderous applause and cheers.
The â€œBad Bloodâ€ singer noted she hadnâ€™t â€œbeen on stage in a very long timeâ€ but that â€œitâ€™s very nice [to be back]â€.
She continued: â€œWhen I heard my girls were playing in London at the O2, I thought, Iâ€™m going to have to see that. And it looks like thereâ€™s about 20,000 other people who also thought that.
â€œSo we had a thought. If we were to do some sort of mash-up, we could possibly maybe get you to sing the loudest you have sung all night,â€ Swift told concert attendees, adding, â€œWhich is a big challenge because you have been singing very loudly â€“ extraordinary work.â€
Then, as promised, Swift and Haim delivered a mash-up of â€œGasolineâ€ and Swiftâ€™s 2016 solo hit â€œLove Storyâ€ amid a frenzy of fan TikToks and thunderous applause.
Fan videos of the performance were posted on social media as those in the attendance at the O2 were left â€œscreamingâ€ over Swiftâ€™s surprise cameo.
Along with a video of the â€œGasolineâ€/â€Love Storyâ€ mash-up, one person wrote: â€œHAIM BROUGHT OUT TAYLOR SWIFT!!! Iâ€™M SCREAMING.â€
Another fan tweeted: â€œTaylor Swift just walked out on stage at the O2 with Haim. Girlfriend is in meltdownâ€.
â€œNo one in the Taylor Swift universe is ever going to know peace now that she went and spontaneously performed with Haim â€“ like she really could show up any place any time,â€ one person commented on Twitter.
Haim opened for Swift during her 1989 tour in 2015. The group also featured on Swiftâ€™s 2020 album evermore, collaborating with the singer on the track â€œNo Body, No Crimeâ€.