Watch Taylor Swift debut 'thanK you aIMee' X 'Mean' mashup for Eras Tour London surprise song

“I’ve never played this one before. Wish me luck,” she said to the Wembley Stadium crowd.

Taylor Swift described London as a “special” location for The Eras Tour during her acoustic performance at Wembley Stadium.

During the second of three shows over the weekend on June 22, the pop star chose to perform a song she had never previously performed live. Additionally, she invited Hayley Williams to join her on stage for a duet.

“We get to play Wembley Stadium eight times this summer. When I’m thinking about that, you think about just being grateful and being thankful,” Swift expressed to the audience, acknowledging their support. (She has three concerts in London this weekend and will return for five more shows at Wembley from August 15-20.)

“On the other hand,”remarked Swift, just before she was about to perform the first of the night's two surprise songs, “it really makes me think about how every time somebody talks s— it just makes me work even harder.”

“I’ve never played this one before. Wish me luck,” she said, before strumming her acoustic guitar and starting "thanK you aIMee" from The Tortured Poets Department: The Anthology.

It was the debut live rendition of the song where she sings, “All that time you were throwin’ punches, I was buildin’ somethin’/ And I can’t forgive the way you made me feel/ Screamed, “F— you, Aimee” to the night sky as the blood was gushin’/ But I can’t forget the way you made me heal.”

“I don’t think you’ve changed much/ And so I changed your name and any real defining clues/ And one day, your kid comes home singin’/ A song that only us two is gonna know is about you,” she continues in a later verse.

Swift performed "thanK you aIMee" combined with "Mean" from Speak Now, both songs celebrating her triumph over critics and adversity.

“Someday I’ll be singing this song at Wembley,” she joked, improvising a line to the tune of "Mean."

To cap off the evening on Saturday, she surprised the audience by inviting Hayley Williams (who had previously performed with Paramore earlier in the show) to join her for a live rendition of "Castles Crumbling," their collaboration from the Speak Now (Taylor’s Version) album. Swift and Williams sat together at the piano, performing the song in harmony.