The Frost/Nixon star told school pals that British world champion Barry Sheene was his uncle, and would even fake his autograph for fellow students.
But he was almost caught out when a paper delivery boy asked his dad if the story was true.
He says, "The most famous Sheen when I was growing up was Barry Sheene, the motorbike racer and a handsome devil he was... A lot of people would say, 'Are you related to Barry Sheene?' And I just couldn't resist and I said, 'Yes I am. I am, he is my uncle'. So it's a little white lie really which kind of spiralled, until eventually people were asking me for his autograph. I used to fake his autograph, bring it in to school.
"I wanted to be liked and so eventually it got to the point when people would say, 'Can you bring some memorabilia back?' and all that and it got way out of control. So one day I was in my living room, there was knock on the door, and my dad opened the door and it was the paper boy coming to collect his money for the round that week and it was a boy from school. I heard him say, 'Is it true that your brother is Barry Sheene?' And I just thought... 'This is it, my life is going to come to an end. Not only will I be in trouble with my father for lying but also my secret will be out in school and that would be terrible'. And my dad went, 'Yes that's right.'"