Liam Payne drinks warm milk and smokes cigarettes while recording new music in the studio.

The 24-year-old singer - who kicked off his solo career this year with 'Strip That Down' - has a number of unusual habits in the studio, according to his 'Bedroom Floor' collaborator Charlie Puth.

Charlie told Billboard: ''I played it for Liam when he was in the studio. And fun fact, he has no air conditioning in the studio. He keeps it at about 80 degrees. He drinks warm milk, I think smokes a bunch of cigarettes, and sings the song perfectly. I don't really understand how that's possible. I mean, it works for him. I don't know if I would be able to pull that off - I go to bed at like, 9 pm every night.''

Charlie also revealed the song was inspired by leprechauns.

He explained: ''That was the most fun I had ever had, writing that record. It was with Little Aaron [Aaron Jennings], Noell [Zancanella], J Kash [Jacob Kashner] and Ammar Malik - really, really talented writers. And we were all at Conway, which is a really nice recording studio. And we were all just messing around; nothing was really coming when we were writing.

''I just pictured what a leprechaun would sing, because I think there were Lucky Charms in the room or I had had them for breakfast. Like, what would a leprechaun melody be? And Noel, who works with Ryan Tedder and OneRepublic, had this cool sound like 'boom boom boom' and I was thinking, 'Oh, it could be like a dance record or something like that.' And out of nowhere, that melody, that joke melody I had, fit perfectly on to one of the dancey chords. The song originally started [with] two parts and we flipped the two parts and then it was over, and we were like, 'Oh it's so great! Your clothes are talking!' We were dancing around, such a fun songwriting session.''

Meanwhile, Liam recently admitted he can't believe how his solo career has taken off.

The One Direction singer is amazed by how well his solo tracks have been received this year and says performing on his own at Wembley Stadium has been one of his highlights of 2017.

He wrote on Instagram: ''I've got to perform to some amazing crowds this year, starting with 80,000 people at Wembley Stadium! With the boys you had the chance to bounce off each other, when you're on your own it's just you and you have to get out and just do it! (sic)''