Niall Horan sent Lewis Capaldi a private message to ask if he'd join him on tour.
Niall Horan
The One Direction singer invited the rising star to support him at his show in Glasgow - the youngster's hometown - earlier this year, and it appears the 'This Town' hitmaker was already a fan of the 22-year-old musician.
Speaking to The Sun newspaper's Bizarre column, Lewis said: "The way he asked me to do it was via Instagram, so basically at this point he's already Tweeted about the music.
"He's been a very vocal supporter of what I'm doing online. It was mad. And ever since then we've just kind of kept in touch."
Lewis - who has also opened up shows for both Sam Smith and Rag'n'Bone Man' - revealed he and Niall, 25, still meet up when they happen to be in Los Angeles.
The 'Someone You Loved' singer - who is currently headlining his own tour across the UK - added: "He's just been f***ing class."
Meanwhile, last month Lewis reflected on his time on the road with Niall and revealed the main lesson he took away was the importance of staying grounded.
He recently said: "Just the fact, he's so nice, do you know what I mean?
"The way someone who's that successful and had done massive things on his own and with One Direction, to still be as humble as he is and as sound as he is is a big thing for me.
"You might get big and become an asshole and there is no reason for it. He's one of the biggest pop singers in the world and you can just sit with him in the pub. The way he treats people around him, no matter who they are, it's all the same soundness. That's all I took away from it."
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