Watch Taylor Swift Join HAIM Onstage For An Iconic Surprise Performance

HAIM fans got a pleasant surprise at the band's show on Thursday night (July 21.) The trio was joined by none other than Taylor Swift for an iconic performance in London.

The "Cruel Summer" singer was thrilled to be back on stage as she joined the HAIM sisters at London’s O2 Arena for a performance of "Gasoline" and a mash-up of "Love Story". “I haven’t been on stage in a very long time," she said per NME. "It’s nice…it’s nice, it’s very nice [to be back]." She continued, "When I heard my girls were playing in London at the O2, I thought, I’m going to have to see that. And it looks like there’s about 20,000 other people who also thought that."

"So we had a thought," she added. "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 – which is a big challenge because you have been singing very loudly – extraordinary work.” HAIM and Swift have collaborated multiple times. The band was featured on her song "No Body, No Crime" and even opened for her 1989 world tour back in 2015.

Watch videos of the surprise performance and a behind-the-scenes TikTok below: