French movie star Vincent Cassel struggled to research his role as the son of a Russian mob general in new movie Eastern Promises because no one would help him infiltrate the Mafia.The Ocean's Thirteen star felt sure he'd have no problems preparing for the part when he discovered he was working among mob bosses on a film project in Dora Fuente, Spain - but the locals wanted to steer clear.Cassel says, "I realised you can't really fool around with those people. You can't just approach them. Before I started doing this movie I was in Spain doing something else. There's a lot of prostitution in Spain, it's legal in a way and it's run by the Russians."There was this little town called Dora Fuente and it's only Russian Mafia people. On the weekend, I'd ask my driver to take me there. I said, 'I need to go and talk,' and he'd say, 'No, I'm not gonna take you there because if they know you're an actor they're gonna kidnap you.' You just don't fool around.It's too violent. It's too intense. "I got close but I didn't have any relationship with them." In the same movie star Viggo Mortensen's make-up was so authentic the Russians on set mistook him for a real Mafia hitman