Dipping into an all-but-forgotten relationship, Taylor Swift graced fans with an oldie but a goodie.

The Grammy Award winner, 34, performed the 2016 Rihanna song 'This Is What You Came For' during her Friday concert in Liverpool, England for the Eras Tour.

She previously wrote the song under the pseudonym Nils Sjöberg with ex-boyfriend Calvin Harris.

'Every single time I have an acoustic set, I'm always trying to think of things you might want to hear — maybe things that might be a little bit unexpected,' Swift prefaced the song. 'Let's see how we did tonight.'

Swift performed the track as a mashup with her song 'Gold Rush' from her 2020 album Evermore. 

The Tortured Poets Department (TPD) artist dated Harris, 40, from March 2015 to June 2016, during which they co-wrote the song.

A source told People at the time that the relationship ended because Harris was 'intimidated' by Swift's success. 

Her rep confirmed the Nils pseudonym was hers in 2016, a month after their split.

Swift performed 'This Is What You Came For' for the first time that October during the Formula 1 US Grand Prix.

After Swift revealed herself as the co-writer, Harris accused her of trying to 'tear him down' in a since-deleted Twitter rant.

'Hurtful to me at this point that her and her team would go so far out of their way to try and make ME look bad at this stage though,' he wrote at the time.

'I figure if you're happy in your new relationship you should focus on that instead of trying to tear your ex bf down for something to do,' the Scottish DJ added.

'I know you're off tour and you need someone new to try and buy like Katy [Perry] ETC but I'm not that guy, sorry,' wrote Harris. 'I won't allow it.'

Harris later admitted his response 'was completely the wrong instinct' in a 2017 interview with British GQ.

'I was protecting what I see as my one talent in the world being belittled,' he said at the time. 'It felt like things were piling on top of me and that was when I snapped.' 

After TTPD dropped in April, Swift shared a statement about letting go of the 'sensational and sorrowful' time that inspired the album.

'This period of the author's life is now over, the chapter closed and boarded up,' she wrote. 'There is nothing to avenge, no scores to settle once wounds have healed.

'And upon further reflection, a good number of them turned out to be self-inflicted,' added Swift.

'This writer is of the firm belief that our tears become holy in the form of ink on a page. Once we have spoken our saddest story, we can be free of it. And then all that's left behind is the tortured poetry.'

The Tortured Poets Department is now available for streaming and download.