Taylor Swift was joined by surprise guest Florence Welch for her first live performance of "Florida!!!" during the final European date of her Eras tour on Tuesday. The pop megastar also debuted "So Long, London", a ballad that fans widely believe is about the end of her relationship with British actor Joe Alwyn, in the acoustic section of the show at Wembley Stadium. Both tracks feature on Swift's eleventh studio album, "The Tortured Poets Department", which was released this year.

Welch, of British indie rock band Florence + the Machine, co-wrote "Florida!!!" and sang on the recorded track. Fans from near and far had travelled to London's Wembley Stadium for the show, Swift's fifth in the British capital in August and eighth this summer, as they snapped up the last opportunity to see her critically acclaimed show in Europe. The London nights followed the cancellation of her shows in Vienna, when a planned attack was foiled by authorities.

Some of the 195,000 disappointed fans in Vienna rushed to buy tickets for the London dates on resale sites, where they were changing hands for up to 10 times face value. Swift told the crowd that she had become the first solo artist to ever play Wembley eight times in a single tour. "We will never, ever be able to thank you enough for it," she said.

Eras, the first tour to surpass $1 billion in revenue, showcases all 11 of Swift's studio albums in dedicated sections. Her performances and the show's staging have been praised by critics. Fans.