The 'Strip That Down' singer has shared some of his memories from his time in the chart-topping boy band to mark their 10th anniversary today (23.07.20).
And Liam, now 26, has admitted he didn't think it would be possible to have someone from ''a whole other country'' in the group.
Appearing on 'Capital Breakfast with Roman Kemp', he spilled: ''At first I don't know why it was so confusing to me that Niall was from Ireland, because I was thinking, 'how is this going to work, he's from like a whole other country, he's not even from nearby, how is this going to happen?!'
''Then I remember we had a conversation straight off the bat, we decided to measure each other's heights because that's how it would be in photos of who would be in the middle ... we were so young though.
''You think you know everything at the time.''
And the 'For You' hitmaker also admitted that he thought their singing in unison was shocking, but the 'What Makes You Beautiful' hitmakers - who formed on 'The X Factor' - didn't ''have the heart'' to tell one another who'd be best at singing the different parts of their songs at first.
He said: ''When we first got together and went down to Harry's house to rehearse, we didn't really have the heart to tell each other who should sing what bit or make cut throat decisions because we were all trying to find their place.
''So we all used to do it in unison, which was the most horrible thing I've ever heard in my life.''
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