The 40-year-old played the role of Obi Wan Kenobi and said he wasn't sure if it was something he wanted to do at first.
In an interview on the BBC's The Graham Norton Show, he said: 'I was a big fan of the films and was really familiar with the first three because my uncle Dennis Lawson had been in them, but when they were casting the new ones it didn't feel like something I was doing at the time.
'I was making British independent films and I didn't think it was really me but as I got closer and closer to being cast in it I wanted to do it more and more so I rang people like Dennis, who said: 'If you want to have a career after 30 don't do it.' Luckily I didn't listen to him.'
The full interview airs on BBC One on Friday July 1 at 10:35pm.