The two stars clashed as they worked on the track All I Ask when Bruno suggested the line "Take me by the hand while we do what lovers do" was outdated, but his songwriting partner dug her heels in and refused to change the lyric.

"We were aiming for that big, diva, ballad thing - that’s what I envisioned," Mars tells Rolling Stone. "But 'lovers'? I don’t know if anybody really says 'lovers' - 'Yeah, we’re lovers'. 'This is my lover'.

"I was like, 'Should we rethink that?' But she (Adele) was so gangster about it. She was like, 'Nope. That’s what it has to be!' And she was right. It's this grand word that makes the song bigger because no one says it. Because nobody talks like that, it pops out. It's not 'what boyfriends-and-girlfriends do' - it’s this over-the-top 'lovers.'"

And Bruno admits he still gets a kick out of playing the track on the piano: "I look forward to singing that part. It’s f**king perfect... Don’t try to be cool. Let it be what it wants to be."