Taylor Swift surprises fans with Paramore’s Hayley Williams at Eras Tour London

Before Williams appeared on stage Swift hinted at a surprise guest, keeping fans eagerly anticipating who it could be.

Taylor Swift continues to delight her fans with unexpected surprise songs!

During the second Eras Tour show in London on Saturday, June 22, Taylor Swift surprised the audience by inviting Hayley Williams from Paramore to join her in performing their Speak Now vault track "Castles Crumbling."

The 14-time Grammy winner left the crowd amazed with this unexpected collaboration.

Fans inside Wembley Stadium shared videos showing Taylor Swift, 34, seated at a piano alongside her longtime friend Hayley Williams, 35, performing the ballad acoustically during the tour's surprise songs segment.

They've been close friends since the beginning of their careers and previously shared the stage in London back in 2011 during the Speak Now Tour.

Before Williams appeared on stage, Swift hinted at a surprise guest, keeping the fans eagerly anticipating who it could be.

“In the process of re-recording, I was really trying to reach out to artists that I'm such a fan of, or in the case of one of the albums, specifically on Speak Now, I reached out to artists who have been so influential in my music, in my writing, who I looked up to,” Swift hinted.

“I asked an artist who I was such a huge fan of to be on one of the songs, and she said yes. London, we are so lucky because when I asked Hayley Williams to come to this show, she said yes.”

During Saturday's concert, Swift debuted "thanK you aIMee" from The Tortured Poets Department, blending it with "Mean" from Speak Now for the first time. In "Mean," she altered the lyrics from "Someday, I'll be livin' in a big, ole city" to “Someday, I'll be singing this song in Wembley.”