Justin Bieber has praised Ed Sheeran as a "super talented songwriter".
The 21-year-old star teamed up with the 24-year-old singer/songwriter for Justin's new track 'Love Yourself' and he was thrilled to work with someone of Ed's "calibre".
Justin said: "He is a good guy, super talented. Really good songwriter so just to be able to work with that calibre of songwriter was really really awesome. We are boys, so we just go out and we're mates."
This is not the first high-profile collaboration for Ed - who also features on backing vocals - as he has written for One Direction and recorded a duet with Taylor Swift.
Justin also admitted that the song - which features lyrics including "You think you broke my heart? Oh girl, for goodness' sake" - is about an ex-girlfriend but he is reluctant to name her publicly because he doesn't want to hurt her.
Co-hosting on Capital FM with Roman Kemp, Justin was asked: "So one of the questions that obviously people naturally ask when listening to a song like 'Love Yourself' - is it about past experiences? Is it about past girlfriends?"
The singer replied: "Yeah, it is but you know I don't want to make anyone upset so I'm not going to say it to the public."
Roman Kemp and Justin Bieber co-hosted on Capital FM, ahead of Justin's performance at Capital's Jingle Bell Ball with Coca-Cola on Sunday 6 December.