Meet Katherine Parkinson, the actress who plays Jen (and knows just as little about computers).

Here, Parkinson reveals what it's like to star in two popular recurring TV series, why The IT crowd is improving with age, and just how remarkably little she knows about computers.

You studied classics at Oxford. Isn't that the sort of thing that marks you out as a future prime minister?

Yes, I did, but that's a bit misleading, because it's not very representative of me or my interests. That's probably why I wanted to do it, to surprise people, which you like doing when you're 18. The problem is, you then realise that it's you who suffers by doing that. I wouldn't say I'm a natural classicist. I wish I'd done English, because anyone who's done that has this amazing reserve of knowledge about all sorts of literature. I can't remember anything, because I crammed it all. But obviously that shouldn't stop me from becoming prime Minister. If only they'd give me a chance

Was it at Oxford that you discovered a passion for acting?

It was. I was hell-bent on going to Oxford because of the opportunities it afforded for acting. I did so many plays there - probably more quantity than quality. It was probably because I felt that as long as I was doing a play I wouldn't have to do any work. I loved it, it was a great time. And if I hadn't gone there, I don't think I would have ever gone into acting.

From there you went on to LAMDA, where you met [IT Crowd co-star] Chris O'Dowd. Did you hit it off straight away?

Yeah, we were friends immediately. He was one of two people that I was very good friends with. I got on so well with him because he was quite irreverent. People took it really seriously, which was the right approach, but could be a bit po-faced. I remember one day we were regressed to children, spending the whole day improvising being children, and he reduced me to tears of laughter, because every time I passed him he would say something really shocking and disgusting, in a sweet little baby voice. It was deeply inappropriate, but it was just so funny.

You left drama school early to do a play. Did you ever have the requisite years of starvation that most actors go through?

I had a bit of that, yes. I've been lucky, but I did have a bits-and-pieces period where there wasn't much steady work. And it's always made worse by your parents and family scrutinising everything you do to see if you're going to make it work as an actor. Their focus can make it seem much worse, having all those people panicking that you're not going to make it.

Obviously you don't need to worry so much now that you've got regular starring roles in two recurring series.

No, it certainly helps. Now if I get a few weeks with no work, I can enjoy it rather than worry about it. Doc Martin came first, I was doing that when I auditioned for The IT Crowd. It's just such a great job, working on Doc Martin - it's great to spend time in Cornwall. I grew up in Tolworth, and didn't see the sea for years on end.

Is it nice to return to projects where you feel comfortable and at home?

People don't realise what a nice thing it is for an actor to go to a job where they know or like everybody, because you're so often having to do new beginnings, starting off on set with people you don't know, having to introduce yourself and make friends. It's the same with The IT Crowd - it's so great that I know Graham [Linehan, the show's writer] and Chris and Richard [Ayodade, co-star] so well. It means all your energy goes into what you're doing, rather than worrying about whether they took something you said the wrong way.

Was it coincidence that you and Chris ended up working together on The IT Crowd?

No. I met Chris for a drink when he was already cast for The IT Crowd. He suggested I go up for the female part, because they were having trouble casting it. I said 'Yeah, yeah, okay,' and he said 'No, ring your agent now!' And I did, and went in and got it. Chris reminds me of that almost daily.

Is it a fairly relaxed experience, then, filming with such good friends?

Yes and no. It can actually be quite frenetic. There's a very haphazard, chaotic process on The IT Crowd, which is really frightening but also really enlivening. Graham's mind is constantly so active, and constantly coming up with improvements and changes, and lines are always changing. You have to be on your toes to keep up with it. It's good for you. Most acting jobs aren't like that, the scripts don't change, it's a much more regimented process.

When fans come up to you in public, can you generally tell before they say anything whether they're fans of Doc Martin or The IT Crowd?

That's a very interesting question, because it's actually one of my favourite games, trying to guess. The demographic for the two shows is so different. Generally if I'm in a pub in Islington it will always be more likely to be The IT Crowd, but up and down the country it'll always be more Doc Martin. With The IT Crowd, now we're on our third series we've got a loyal audience, and that's great, but I think we'd love to break through to a pan-generational audience. I think that's always been Graham's intention, to make it a proper family sitcom.

Is it fair to say that the second series of The IT Crowd was better than the first?

Yes, I think so. And I think the third series is probably even better than the second. I think it's found its feet. We all know each other, we know how to work together, we know what we're doing, we know our characters better, Graham knows the characters better. I think it's bound to be the case as you go on. I mean, I'm sure there are some comedies that know themselves totally right from the first series, but I think most take a little time to find their feet. I think it's made it a very satisfying process, because I feel like we're really getting results more and more as we go along.

The audiences must react differently after the first series, because now anyone who comes to see the recording is bound to be a fan of the show. Does that make your job easier, performing in that environment?

It does and it doesn't. It's great to have an audience there, people who know the show so well. But the thing you have to remember is that you don't want to alienate potential new audience members at home. We don't want too many in-jokes which you only get if you watched episode three of the second series, and with the studio audience all roaring with knowing laughter while people at home don't get it. But it's very important to have that loyal fan base, and we're very grateful to them. But you don't want to end up thinking a joke is funnier than it is just because it's gone down well in the studio.

Filming in front of a studio audience is quite unusual these days. Why go to the bother?

It is quite unusual, it's true, but I think there's a move back in that direction. Studio-based sitcoms have become synonymous with slightly dated stuff, and so many of the modern sitcoms like Gavin and Stacey and Pulling don't use a studio. But Graham would never work any other way, and his writing really suit's a studio setting. You need the audience's laughter to punctuate the script. The audience are part of it. We're all required to give quite big comic performances, and the audience really helps with that. You really realise that when you film the stuff that's not in the studio - it's like filming a totally different show.

With so many inspired comic moments, and a studio audience in the mix, do any of you have problems with corpsing?

Oh God yeah. We had it particularly badly on the Friendface episode. I don't want to point fingers, but the thing is, when Richard gets the giggles, you probably wouldn't notice. But Chris and I will know, and then it makes us go. There's a whole section in the Friendface where Moss and I are at a party, and I hope you won't be able to see us laughing in that, because I can't remember there being a take completely free of it. I'm sure they'll work round it. But yeah, it happens, and it happens more on this show than any other job I've ever done.

Lastly, Jen obviously knows nothing about IT. How are you with computers?

Well, I'm actually sitting at my computer now, but I'm afraid I'm so backward I sometimes see Graham blanch when he realises that I've never heard of Vista or something. But I'm going to get myself one of those, um, movable computers - what do you call them...? Laptops! I am bad. I still call my radio a wireless.