London, UK - Taylor Swift made her return to London extra-special with a surprise duet alongside her long-time pal and fellow musician, Ed Sheeran.

On Thursday, the 34-year-old pop star performed her first of five sold-out shows at Wembley Stadium – and her first performance since a confirmed ISIS terror plot led to the cancellation of her three shows in Vienna earlier this month.

When the acoustic set rolled around, Taylor proved to have more surprises up her sleeves than just her song selections!

Ed was welcomed to the stage for the guitar performance, which was a mashup of Everything Has Changed, End Game, and Thinking Out Loud.

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The first two songs are both collaborations between the pair from Taylor's discography, while Thinking Out Loud is the chart-topping hit from the 33-year-old Brit's 2014 album ×.

The Karma singer gushed over Ed to the crowd, calling him a "second brother" to her.

Unfortunately, the 34-year-old athlete wasn't in attendance at his girlfriend's latest show, as he's back to business with the Kansas City Chiefs for the NFL preseason.