Taylor Swift: Singer surprised fans at The 1975 concert

Taylor is preparing for her own tour in March of this year

Have you ever been to a concert, enjoying the performances from your fave band or singer - and then they bring on a surprise guest?

That's exactly what happened to fans who were enjoying a concert from the band The 1975 in London last week.

When none other than Tay Tay came on stage, and treated fans to the first live performance of her song Anti-Hero and a cover of The 1975's song The City.

The gig was taking place at the O2 Arena on Wednesday as part of the band's At Their Very Best tour.

Have you ever been to a concert and a surprise guest came out? If so let us know in the comments.

How did Taylor end up playing at 1975's concert?

The 1975 formed in 2002 and is made up of Ross MacDonald, Matthew Healy, George Daniel and Adam Hann.

It seems like Taylor Swift has long been a fan of the band after being pictured at one of their shows back in 2015, as well as wearing a T-shirt with the band's name on it.

Lead singer of the 1975 Matt Healy has also been seen wearing a T-shirt promoting Taylor's 1989 album.

Taylor and Matt Healey have been friends for a while, pictured here at a party in 2015 alongside Ellie Goulding and former Radio 1 Breakfast Show host Nick Grimshaw

Now it seems the two have also been working together, with Matt revealing last year that the band collaborated with the 33-year-old singer on her hit album Midnight.

Sadly none of the songs they worked on together made the final cut, but it seems like there are no hard feelings between them.

Fans took to social media to express their shock by her appearance, with many calling it "the best thing ever!".

One fan said: "The 1975 concert became a Taylor Swift concert ????????"

Another wrote: "Now my sister who doesn't even like Taylor has just seen her live and I am in bed. Why is life so unfair? Never been more forward about admitting just how jealous I am."

The band posted a video of the performance on their social media, where Taylor can be seen at the front with her guitar

Taylor will be starting her own tour later this year, which will be her first in five years.

Announcing the news on social media, Taylor shared a tour poster with the caption: "I'm enchanted to announce my next tour: Taylor Swift The Eras Tour, a journey through the musical eras of my career (past & present!).

Fans immediately took to social media to share videos and photos from the arena.

"The first leg of the tour will be in stadiums across the US, with international dates to be announced as soon as we can!"

Taylor will be joined by a number of popular artists, including Paramore, Haim, Phoebe Bridgers and Gracie Abrams.

We can't help but wonder if she'll have a couple of surprise guests up her sleeve too!

Have you been lucky enough to see a surprise guest perform? If so who? Let us know in the comments.