Taylor Swift startled London’s O2 Arena by playing with Haim, and it’s safe to say that the Swifties are not calm.

The American pop queen has been maintaining a low profile recently, and we can’t blame her for enjoying the downtime after the success of her lockdown albums and re-recordings of her current catalog.

But, in classic T Swizzle fashion, she always appears when you least expect it, and that’s precisely what fans were treated to on Thursday night when they arrived for what they thought was just a Haim concert in the capital.

Estee, Danielle, and Alana are now on their One More Haim Tour, having returned to the UK following their incredible performance at the Glastonbury Festival.

The crowd exploded in screaming when the Blank Space hitmaker went out to deliver a spectacular mash-up of Haim’s Gasoline and Taylor’s country song Love Story.

‘Wait, you guys, we’re in London, so we can’t play in London unless we bring out a special visitor,’ the sisters teased.

Taylor Swift joined Haim for a surprise concert in London.She blasted out the notes! (Picture: Twitter)

Taylor Swift joined Haim for a surprise concert in London.Taylor looked amazing in an all-black outfit and her usual red lipstick. (Picture: Twitter)

‘Not only is the person I’m about to introduce the most great singer, songwriter, producer, and overall amazing person, but she’s also one of our close friends. So, O2 Arena, will you kindly welcome Taylor Swift to the stage?’ they said eagerly, before the venue lost all of its cold.

The foursome looked incredibly stylish in identical black attire, with the Haim sisters wearing their signature black bikini tops and slacks.

Taylor, on the other hand, wore a black crop top and high-waisted leather slacks, exuding rock cool.

She brushed her hair back into a braid and, of course, wore her signature red lipstick.

After their performance and before leaving the stage, the friends enjoyed a lovely group hug, with Taylor beaming from ear to ear as she waved fans off.

Taylor later shared a humorous TikTok video of the singers preparing to perform on stage.

She played a children’s Copycat song in the background, making fun of how she was emulating their attire.

This isn’t the first time the Haim trio has performed with Taylor; in fact, they’ve been friends for years.

Estee, Danielle, and Alana appeared as special guests on Taylor’s 1989 Tour in 2014, where they also collaborated with Nelly on a performance of Hot In Herre.

Taylor Swift, Haim, and Nelly.The Haim sisters joined Taylor as a special guest, along with Nelly, for her 1989 tour.

Haim also provides backing vocals on No Body, No Crime from Taylor’s Grammy-winning album Folklore, with Estee receiving a special mention in the lyrics.

‘Este’s a friend of mine; we meet every Tuesday night for dinner and a glass of wine,’ Taylor says in the song inspired by her love of crime thrillers.