You act, write and present television shows. How would you define yourself?
I'm an actor. Those other things, I just see them as fun opportunities. I'm very proud of Gavin and Stacey, but I think I have to write something else even to start to consider myself a writer. Just because you do something once, it doesn't mean that's who you are. I played football last night; it doesn't mean I'm a footballer.
In another life, what would you have done?
I don't remember a time when I wanted to do anything else. All I've ever wanted to do was perform, in whatever capacity. I've always been an attention-seeker. The truth is, I'm useless at everything else.
You got your break in The History Boys at the National Theatre. What's it like to be back?
That was the moment my life changed, so to be back there is fantastic. But I was also a little apprehensive because, before, I was with these seven other boys. It felt a bit strange to walk down the corridors without them.
Is the thought of a live audience intimidating?
Learning it all is a big thing: I've got to learn two hours of dialogue. I can't tell you how nervous I am; but you can't overestimate quite how nervous I get about everything. I got nervous before this interview.
Have you always suffered from nerves?
I don't know anyone who doesn't. Richard Griffiths told me that he once saw Laurence Olivier physically shaking in the wings. Nerves are good - you're only nervous when something matters.
Do you worry about what people think of you?
You can't be worried. Often, people's best work is their first and that's because they're not thinking about how people will react.
Are you politically engaged?
It's a tough one for me, politics. I grew up in a house where my father is a Christian book salesman and a Tory and my mum's a social worker. So I can always see the benefits of both arguments.
Was there much political debate at home?
Like you wouldn't believe. My mum is dealing with people who rely on the state. And my dad says, "Well, it's my money." My dad came from a working-class background and has done all right, but he's not one of those awful Tories. He doesn't want anyone to be castrated.
Do you vote?
I have voted. I don't think it would be right to tell you who for. I haven't always voted for the same party, mostly because I find that strange. One thing I've never quite understood is when people say "I'm a Conservative" or "I'm Labour", before even hearing what the person running stands for or wants to change.
So you wouldn't describe yourself as tribal?
Not at all. I think it's odd that people would be - we might as well take votes from everyone at 18 and then consider their votes the same until they die. I can be swung, is what I'm saying.
What does God mean to you?
Here's the thing. I grew up in a Salvation Army family. We went to church every week. But my feeling is that faith is separate from the Church.
It's personal, while the Church is organised by a group of people and stuff will go wrong, because people always make mistakes. When I look back at the Church I grew up in, I realise that nothing about its behaviour was very Christian. It was just a social club on Sundays where people would meet up with their mates.
So you're not a believer?
I don't mess with science. Creation and all those things: I get it. I would never argue with the facts. But I have a hunch that there must be something else. It's inconceivable to me that this is all for nothing. I'm looking forward to finding out - but not just yet. I need to get this play finished, at least.
Is there anything you would like to forget?
Lesbian Vampire Killers? I wouldn't mind forgetting that. It was never quite the film we thought we'd signed up for, but then I'm not sure what we thought we were doing with a title like that.
Has there ever been a plan?
My plan was always to maximise fun: to enjoy whatever I'm doing. It just seems so pointless if I'm not.
Are we all doomed?
I don't think so. Most people are all right. There will always be a few dicks that ruin it, but the best thing we can do is ignore them. Imagine
if, in that big space in Tate Modern, there was a floating ball, held up by gas. From the outside, it looks blue and green but, when you get closer, you see that there are millions of tiny people inside, all doing great things, making each other laugh, falling in love, creating other people.
You'd go: "Oh, my God, this is amazing! You have to go to see it." We would queue around the block. And that's us: we're all doing that.
1978 Born in Buckinghamshire
1997 Makes film debut in Shane Meadows's Twenty-Four Seven
2004 Plays Timms in London production of Alan Bennett's The History Boys
2007 Writes and acts in Gavin and Stacey
2009 Stars in the comedy horror film Lesbian Vampire Killers
2011 Takes part in his third Comic Relief. Plays the lead in Richard Bean's One Man, Two Guvnors at the National Theatre