Tim Minchin versus the Sydney Symphony

Tim Minchin is a hugely successful comedian and acclaimed musician; he's recently played to 16,000 people at London's O2 Arena, he's just written the music for the Royal Shakespeare Company's much-anticipated production of Roald Dahl's Matilda; and he's about to come back home for a tour accompanied by an entire orchestra. He doesn't do things by halves, this boy.

How did you deal with the thought of 16,000 people seeing you perform? I think a lot of people don't really think about what that would do to their ego. They just think: Well, that guy's turned into a bit of a cunt. Not that I've given people reason to think I've turned into a bit of a cunt, but it changes you. You either get scared or you convince yourself you deserve it – even if it's an exercise in self-delusion. I oscillate between the two states. Sometimes I think: you know, I'm fucking good at this – of course 16,000 people are going to come see me. But then, in the middle of the night when you wake up and can't get back to sleep you can lie there scared shitless.

Do you get recognised a lot? Yes, but it's not a problem. When it first started to happen I was like "God this is a head-fuck!" But somewhere along the way in the past year I've just forgotten about it. Besides, if I wear my glasses and pull my hood up nobody notices me.

Do you worry about the impact of your fame on your family [Tim and his wife Sarah have a daughter, Violet and a son, Casper]? I'm probably a bit in denial about it because, ultimately, what can you do? The only risk comes when, because I'm so opinionated, the kids get to an age where they can Google me and see some fairly nasty stuff about me because of something I might have written a song about.

Like 'Pope Song' ["If you cover for another motherfucker who's a kiddie-fucker, fuck you/You're no better than the motherfucking rapist..."]? 'Yep, that would be the kind of thing. That song's actually an examination of what we find offensive. It challenges people who find that language more offensive than the act. I'm constantly outraged by that. If you listen to the song carefully, it justifies its language: this is the language you should use when you're angry at kiddie-fucking.

Many comics tone down their material when they become famous, but you seem to have become even more outspoken. I feel that the bigger the audience, the bigger the obligation I have to say something I think is important. I've always written material about religion. I think it grew from my shock as a kid that adults actually believed this stuff – and from there I got more and more into science, secularism and rationalism. Some of the things I sing about are contentious, but I seem to get away with it by being cheeky and charming - at least that's the theory. I'll play ‘Pope Song' to 16,000 people and hopefully I won't lose more than ten of them.

In the past you've said you "tread the line between self-mockery and wanting to be an iconic figure". Is it hard to hold on to your perspective now you're playing arenas and venues like the Opera House Concert Hall? Definitely. I'm never sure of the level to which I'm taking the piss with the rock-star posturing – taking the piss out of rock stars while I'm sort of becoming one. But what I can do is mock the idea of grandeur – hence having a 55-piece orchestra on stage with me.