He's been a comedian. He's been a cop. He's been a killer. He's been a Charlie Chaplin. He's even been in prison (for real). Now, Robert Downey Jr. is Iron Man and he's having the time of his life...

Robert Downey Jr.'s been a bad boy. Everyone knows about his spells in jail, his battle with drugs and his wild, uncontrollable talent. He's had second, third, fourth chances at his career in movies and in television (remember his stint alongside Calista Flockhart in Ally McBeal?). Whenever someone needed a singular figure, an explosive character, someone with some indefinable.. cool, Downey Jr. managed to keep working. And now he's finally hit the big time. Clean and sober, a martial arts student and happily married, Downey Jr. has channeled his nervous energy into his work and it's paid off in spades.

When Elf and Swingers man, Jon Favreau, got the gig directing Marvel's Iron Man, he knew he needed someone special, someone with a twinkle in their eye to bring charming alcoholic industrialist Tony Stark to life. Someone who could emotionally mobilise Stark's journey from selfish weapons manufacturer to metal-clad superhero with a conscience. Downey Jr. did just that and then some. So, with his first blockbuster on his hands, the most gifted actor of his generation is finally back on track and he's all about the work, baby...

You've been pretty busy recently.

Yup. Finished Iron Man; two weeks later started Tropic Thunder, finished that; started shooting The Soloist; then Sherlock Holmes with Guy Ritchie. I've gone from action to comedy to drama to action - I haven't had a day off since November 2006! They call that the old back-to-back-to-back experience. Not for the weak.

You've said previously that you lobbied to play Iron Man because you were tired of making movies that nobody saw. How did you prepare for the shift from indie and arthouse films to blockbuster filmmaking?

I just had to buy into the idea that I could play the kind of guy that I love to watch in movies like this. And all you've got to do is not be supid and silly. Take what you're doing seriously. When you're supposed to say something really butch, don't laugh at yourself. I was like, "I'm gonna get this sooooo dialled in that somebody else, literally, would have to be crazy to be as ready as me."

What do you like most about the character, Iron Man's alter ego, Tony Stark?

He has become lonely in all of his glory, in all of his material success and influence. When you see this guy in his workshop, you realise his best friends are computers and robots and this is someone who really needs to get a life. He needs to do something worthwhile because what he has been doing, building a better mousetrap of death, isn't any way to live. He has real issues. And he's funny and very cool.

How did you find the suit? Comfy?

When they unveiled the suit in the movie... I was overwhelmed. The suit is supposed to be iron... you can imagine the consequences! I only wore the whole thing once or twice but me and the stunt guys were all a bit different physically - I had an average-size head but wasn't as tall. I have bigger arms, which made it easier for them to get their arms in the suit, but then the helmet hurt one of the guy's head. And the other helmet had plenty of room but the shoes were too small. The Mark I suit was like 70 pounds and the Mark II and III were something like 55 or 45 pounds. Oftentimes you weren't wearing the whole thing and by the end they'd be like, "Bring Iron Man to set!" And I would just come to set in a tracksuit going, "Here I am!" because I couldn't take any more abuse!

Now when you're successful, is the temptation to work until you drop?

Yeah. I cannot deny that the opportunity to do Iron Man and create a franchise thing, then go do a really big, epic comedy with Ben Stiller, and then to go from that into doing a drama with the guy who did Atonement with Jamie Foxx was unbelievable. It's like, "When is this ever gonna happen again?

And you've had a long career already.

Twenty-five years ago was Weird Science with John Hughes, the first time I was in a studio movie. 1 met Joel Silver on it, who I did Kiss Kiss, Bang Bang with years later, which was the movie that had Jon Favreau saying, "Maybe this guy can do something with Iron Man." None of my other movies had really demonstrated that and not many people saw Kiss Kiss. But Jon did.

Presumably you're being offered every script in Hollywood now. How do you choose what to do next?

I always wind up throwing the script across the room and going, "When do we start?' because momma needs a new pair of shoes and I don't have real estate in Studio City that I'm renting out or whatever. I'm a working dad. What drives me is the promise of the real American dream - that you don't have to retire but when you're 65 you have somewhere to retire to if you want. Start a garden or write a book that somebody or nobody reads or whatever you want. In a way it's like getting the proverbial gold watch. The watch is not the thing: it's that people appreciate you. It would be crappy if 25 years later you get a cheapo watch. But I'd survive even that.