Rafe Spall's latest character, Pete, the eponymous lead in the new Channel 4 sitcom Pete Versus Life, is a feckless loser with a non-existent career, a disastrous love life, and an astounding degree of social ineptitude. Just as well, then, that Spall is such a good actor, because his own life could not be more different. Everything is rosy in the Spall garden. His career trajectory seems to be permanently in the ascendant, with hits on stage as well as screens both big and small. And as for social ineptitude - well, as an interviewee he's confident and charming, a far cry from the gaffe-prone idiocy of the hapless Pete.

Here, Rafe discusses the joys of playing Pete, how he got into acting to impress the girls, and why he can relate to Pete's tendency to sit around for hours on end watching daytime television...

Hi Rafe. Your new sitcom is Pete Verus Life. What's it all about?

It follows the life of a twenty-something sports journalist called Pete Griffiths. He gets himself into all sorts of uncomfortable, cringeworthy, embarrassing situations. The clever conceit of it is that his life is commentated on by two football commentators, who comment on the mundanities of his life, from his relationships with girls to going to lunch at his parents' house. It's so well written, it's really funny. I think an inspiration for it was Curb Your Enthusiasm - just the cringeworthy, terrible situations you can get yourself into. A really interesting thing about playing Pete is that he's so amoral, and yet you can't help but like him. That was a thing I wanted to do when I took on the part, I wanted to play this character who is, on paper, quite hateful, and lets himself down at every juncture, and yet you kind of want to root for him.

That must be a difficult trick to pull off as an actor?

It is a difficult balance, and me and the writers and the producer and director all thought that was so important, that he needed to be someone that you would like. The thing about Pete is that he goes into things with the best of intentions. And he's a nice enough bloke, he's not a bad bloke, he's just a bit of a liar, really. He gets himself into terrible situations by lying, and it's lies upon lies upon lies. Most of the time, when he gets himself into these situations, he is actually trying to help other people. It's a bit like Larry David - he always gets into trouble by trying to help other people.

Pete's fairly unsuccessful, and drifts along through life quite a bit. I imagine a lot of actors have that experience at certain points in their career. Have you had patches like that without work?

Oh God yeah. Of course. Early on especially, and I'm sure there'll be times like that again. No matter how successful you are, you'll always have four month periods or whatever where you're not doing anything, and your life revolves around getting up at 11am and watching the end of This Morning, and then Loose Women, and then having lunch, and then lying about. You cease to be a functioning member of society. You end up living in your pyjamas. It can be quite depressing. So I can identify with that aspect of Pete's life, in terms of being a bit of a waster. Especially when I was a teenager, and I'd watch television for nine hour marathons, watching daytime television. It gets bad when you know the schedule, and you know when to turn over because there's about to be the repeat of Cheers on Channel 4, and then A Place in the Sun. When you know that, you've got to dust yourself off and go out.

Pete's a sportswriter, and obviously he's having his life commentated on. Are you a sports fan?

Oh yeah, massive. I love all sports. I've been loving the World Cup. I've been lapping up every minute of it.

With a show like this, how much do you stick to the script, and how much do you improvise?

Generally, because Bert Tyler-Moore and George Jeffries have written such a clever script, you don't need to improvise. What they've done is so funny. But there were definitely occasions where we could try things and change stuff. The writers were there on the set the whole time, so if anything needed changing, they'd come up with great stuff on the day. That was one of the joys of having them there. If a scene wasn't working, or we needed to do it a different way, they were there to help. There are definite moments of improvisation.

Apart from all your lounging about with Pete, is there anything else of you in him?

He's got the same hair as me. We've got the same voice and the same face, as well, but there's not a lot of me in there.

You're not crushingly socially inept?

I'm not crushingly socially inept, and I'm not amoral, and I've never denied my parents. No, I really hope there's nothing much of me in there.

Your career's taken in drama and comedy on stage, film and TV. Do you have a favourite genre or medium?

No, not really, it's just about good scripts. I'm lucky enough to be able to choose what I do at the moment, and I just choose things because I think they're good. I did Pete Versus Life because it was really bloody funny and it made me laugh, and it was clever and great. Everything I've done over the last few years I've gone into with the best of intentions, in terms of it being a good script and believing it to be a worthy bit of work, whether it's comedy or drama, stage of film. I don't really care if it's on TV or on stage, or if it's a comedy or a drama, I really enjoy them all.

And how much did you enjoy doing Pete Versus Life?

It was the most fun I've ever had doing a job. To do a straight up comedy was brilliant, I loved it, absolutely loved it.

Did you always know you were going to end up in acting, with your family connections?

Yeah, definitely. As long as I knew you had to do anything in life, I was going to be an actor. It was always in me. Obviously it's because I grew up around it, but then I've got two sisters who don't act. What my dad always said to me is "You can't just want to do it, you've got to need to do it." I think that's true. It's in me, and it's what I have to do. I didn't do very well at school, and the only thing I ever really excelled in was acting. I'm very lucky to be able to make a living out of it.

You talk about 'needing' to act, but your motives weren't always so pure. I read that you loved your first role in a school play because it got you a girlfriend...

Yeah, yeah, yeah, that's true. I played fat Sam in Bugsy Malone, and one of the prettiest girls in the year phoned me up and said "I just saw you as Fat Sam. Will you go out with me?" I was like "Yeah! Fantastic." And that led to my first kiss. And I thought "Wow, this is a way for a fat kid to get girls." Which there aren't many. So it worked for me.

You were quite a bit bigger when you were younger. Did you really lose five-and-a-half stone in three years?

Yeah, I did. It's pretty easy. You eat less and you move more. I stopped watching loads of television and I went to the gym. And I stopped eating seven chocolate bars-a-day. It's a bore having to watch your weight, but it's changed my life and my career.

Yours is a career where how you look makes a massive difference to how well you do, doesn't it?

Yeah, totally, totally. I've just played William Shakespeare in a Roland Emmerich movie, and I don't think I would have been cast as that had I been five stone bigger.

Do you feel that you have to continually prove yourself because of your surname?

I think I used to, but now not so much. I sort of think I have. Not because I've been brilliant, but because I've stuck around for seven or eight years, and I've gone far enough now to know that I can make a living out of it, and people think I'm good enough to employ. I've proved to myself - which is the most important thing - that I don't need to trade on my dad's name. I don't need to prove it to anyone else. I'm not denying that, early on, it gets you in the door having a famous dad - but once you get in the door you've got to do the business. I did do that, and I worked really hard, and I'm proud of myself.

So what are the roles that you've done that you're proudest of?

I did an ITV drama called He Kills Coppers which I was really proud of. I'm proud of everything I'm in - not because of me, but because of the quality of the stuff I've been in of late. I'm really proud to be associated with good work and good people. Most of the things I've done in the last few years - whether it be a big film or a BBC4 drama, I've been proud of. Everything I've done, I've been proud to put my name to.

What are your career ambitions?

Just to carry on doing good work - just to carry on doing work that I care about. I want to play good parts in good things. This has been an amazing year for me. I want to carry on making a living at what I love doing. And as long as I carry on making a living, then I'll be a happy man.