Taylor was on stage at Wembley Arena when she decided to sing something a little different.
Telling the crowd she wanted to sing something unexpected, she began to play the opening notes of Robbie Williams classic Angels.
Robbie, wearing a T-shirt with Taylors face on it, then emerged from the floor in front of Taylors piano, and the two popstars sang together.
Taylor, in a long black dress that was split to her thigh, later left the piano and walked with Robbie down the stage to really belt it out for the crowd.
It came after she was joined by former One Direction star Niall Horan on stage the night before.
Niall and Taylor performed his track Slow Hands together.
She then shared a picture of the two of them in rehearsals, saying: Soundcheck at Wembley Stadium with this guy @niallhoran THANK YOU for surprising the crowd tonight!!!.
Earlier this month, Taylor took time out of her show to pay tribute to the victims of the Manchester Arena bombing.
The star was performing at the Ethiad Stadium in the city when she thanked fans for their incredible resilience to keep dancing and to keep the innocence and the joy and excitement.
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She told the crowd: Concerts are supposed to be about to innocence and joy and excitement and escaping things that stress us out, and what happened over a year ago was to try and steal that excitement and joy and escape, and ever since then youve shown such strength and youve shown you will never let anyone forget those victims,
And youve shown you have such incredible resilience to keep dancing and to keep the innocence and the joy and excitement.