One Direction song dedicated to Liam Payne's girlfriend

Liam Payne's relationship with his girlfriend Sophia Smith is detailed in a special song on One Direction's new album.

The Story Of My Life hitmakers' track Illusion, which features on the band's new album Four, is about Payne's longtime romance with former school mate Smith.

Payne reveals the band's collaborator, Julian Bunetta wrote the song after they had a heart-to-heart chat.

He tells Australian website News.com, "There's a song on the album which is completely about Soph, it's called Illusion and funnily enough, I didn't write it... I was having a chat with Julian, we were both talking about our girlfriends and I left him at it and he wrote all the words based on mine and Soph's relationship. It's all based on things about us."

Four is due for release later this month (Nov14).