It's always nice to be challenged.

I take my hat off to the ladies. The amount of grooming-plucking and shaving and all the other things men never have to do. I went down and spent time with transvestites in London in the clubs and all that. Got an insight to that world, and it's a mad world, but they are very warm and very open people. It was a great experience.

But television affords you, what you just described, to - over the course of 18 hours, now that we're doing a third season - tell the story of this man. You're not under any obligation, really, to do massive expositional stuff at the beginning. You're at liberty to say, "Come with us on this journey," and, gradually, you become aware of what his motivations are, what drives him, what his weaknesses are, what his strengths are. That's what I think's sucking people into these worlds, because it is kind of like a novel, you just go really, really deep.

At the moment I'm doing this space movie, so I'm obsessed with physics and space travel. I know three months down the line it's gone. Then I'll be able to superficially say stuff about space.

All I've tried to do as an actor is follow the good writing. That's been my main drive. It's not always possible, so when you do come upon it, like when I came upon this, you realize pretty quickly this is something you need to be involved with.

I think if you play characters, it's very important not to ever tag them with any sort of disorder, or diagnose them, or whatever. You have to normalize the behavior to get inside the character.

It's a very organic kind of way that people are discovering it, by word of mouth, which I always think is the best way for things to grow. In terms of the affect it's been having on me, I don't even notice that. It's lovely to be able to talk about a piece of work that you're very proud of, that I think's a complex piece of work and not superficial and has depth to it.