Totally not being a part of the European leg of her tour, the London native stopped by and surprised Taylor's fans with an appearance and awesome duet.
The two BFFs serenaded the crowd with Ed's hit song "Lego House" and it was pretty much amazing. As we all know, Taylor loves to surprise her fans with guest appearances at her shows and this just happened to be one of the best ones.
"First night in London and @edsheeran came out to surprise the crowd with 'Lego House'. Earth-shattering screams ensued. What a lad. #redtour," Taylor wrote on Twitter after the show.
Ed added, "Sung Lego house for the first time ever with a band tonight with @taylorswift13 at her London show. Orsum, thanks for all the love."
Things weren't as cool for Taylor later in the show when a fan bombarded the stage. Read about that here.
What do you think about Ed and Tay's version of "Lego House"?
Watch Ed and Taylor sing "Lego House" from her O2 Arena show below.