The American songwriter has spoken out about working with the One Direction star on their ''beautiful'' song 'Not Our Fault', which they produced last summer with Ed Sheeran's writing partner Jake Gosling.
Gavin was really impressed with Harry's musical talent but also found himself fawning over the pop hunk's floppy locks.
Gavin said: ''(He's an) absolutely talented person; awesome hairdo, right? ... I'd only heard good things about Harry from other people that I knew ... I think it's important to diversify if you can ... We got in the studio and he was really respectful, he was nice. I played for a second; I sang an opening line and he immediately followed it up with another line. A few hours later we had the majority of a song completed - it's beautiful.''
The 'I Don't Want to Be' singer also revealed the pair's track is about a failed relationship, but is adamant it isn't about any of Harry's past conquests - who include Taylor Swift, Caroline Flack and Kendall Jenner - but more about the musical duo's lifestyles.
Speaking to Access Hollywood, Gavin said: ''It's about if it doesn't work out sometimes you can't necessarily just blame it on yourself. ''Sometimes it's what's going on around you and other things that have nothing to do with the two people involved; it touches on that subject. It's a story for people who do a lot of travelling and have the lifestyles that we have.''
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