The 57-year-old actor - who plays the role of Russian bad guy Ivan Vanko (Whiplash) in the film - went to Betyrka prison in Russia to research his role, and got on well with one of the inmates. He said: "I saw a lot there at the prison - and I got a lot more. I talked to a guy at Russia, in my hotel, who had just gotten out two weeks earlier - we spent a couple of hours together, and in those two hours he took his clothes off and showed me all the crazy tattoos he had. "He told me what the tattoos meant and talked about some of the businesses he was involved in over the years, some of the crimes he`d partaken in and what his ranking was in the prison. I found that interesting." The Oscar-nominated star also had to work out to lose weight he had gained while making `The Wrestler` to play the role. He told film website MovieHole: "I had to take off a lot of weight after `The Wrestler`, so when I got this I had to wear a muscle suit - which weighed about forty pounds. But yeah, I had to work out for a couple of months - I was on the treadmill every day - if only so I could carry that heavy vest around. `Iron Man 2` is released in the UK on April 30.