Shawn Mendes brought out Niall Horan at his show in London for a surprise duet of "This Town." "I'll remember this for a long ...

Last year, Mendes made a surprise appearance to perform "Treat You Better" during Horan's headlining show in London ...

Shawn Mendes invited former One Direction singer Niall Horan to join him for a surprise duet of Horan's debut solo single ...