Like everyone else in the country, Pauline McLynn has been feeling the cold a bit of late. The actress has spent the last few months filming the seventh series of Shameless. "It was freezing today. I'm only just thawing out," she laughs. But, in spite of her chill, McLynn exudes warmth and good-humour as she discusses her new role, as well as her successful writing career and why she will always be grateful to Mrs Doyle, her infamous turn in Father Ted...

You're in the new series of Shameless, and you're playing Libby. What's her story?

Libby's a librarian, whose life Frank saves one day on the street. And they fall in love pretty much instantly. Who would have thought it? Frank, in love?

Not just in love, but in love with a librarian!

Well, I think words are pretty dear to Frank's heart. He can talk himself into or out of any situation. He's one of those characters who's just chosen the dark path. It's clear from the fact that he has a genius son that he could have been that as well. He just prefers drinking and drugs. These are the choices we make.

Playing Frank Gallagher's love interest - that's some role!

It is! And to be honest with you, I was already a huge fan of the show anyway. And I'm a huge fan of David Threlfall. The fact that I get to go out playing with him? Are you joking me? It's bloody brilliant. But it's quite strange being opposite one of the most iconic television characters in the world. You have to raise your game.

Does it make it more difficult in some ways, having been a fan of the show, to come in and act on it?

It's difficult for anybody when they come on to a show that's been going for so long - this is series seven - you have to hit the ground running. Everyone else knows what they're up to. And you know what they've been up to as well, because you've been watching them for years. But that's odd, coming in to a cast that's already so established. But it's been brilliant as well - there's no time for faffing around, you just get in and go for it. I hope people will like the result. I'm certainly having a ball doing it. The vast cry of joy that is Shameless, the cry for humanity, it is as brilliant as that to make. Every day is a great day.

Libby's a librarian. That brings to mind a rather dowdy, meek character. Can she hold her own against Frank?

I think she's a bit feistier than that. Maybe that's me bringing a little of that along with me! The first description of Libby that I ever saw was that she's a fetishist's dream of what a librarian should be, so we went for the full corset job, the glasses, the killer heels, and she goes around quoting poetry. And of course Frank's well able to join in with that, he's so intelligent. So initially they speak to each other in high romance - I will even say the word 'Byron' out loud to you! There's a load of that. So she's not a regular idea of what a librarian is.

When we started, we filmed in a library. Thanks be to God, some of my own books were on the shelves, and the man who was running the library was very good. He said to me "They go out nicely!" But anyway, he and the two female librarians who were there came over in a break in filming and said "Can we just say that we think it's brilliant that you're a glamorous librarian." So for all that I wear glasses some of the time, for me this is the most glamouous role that I've ever played. There are some gorgeous costumes.

Glamorous? Really? Playing a librarian who goes to bed with Frank Gallagher?

You see? You can have it all! You do wonder though, how does Frank do it? He must be demon good in bed. I imagine he is.

Is it weird, acting opposite him while he's directing?

He directed the first episode of the series, and in many ways I found that incredibly helpful. I'd only done one previous thing with David, which was a radio series called Baldi which he did on Radio 4, and I was in a few episodes of that. So I sort of knew him - and he's one of those guys that you have an instant rapport with anyway - and because he started life as an actor he's incredibly generous as a director, and I really trusted him to see me through that first episode. Occasionally he'd disappear for a little while, and that was him off checking on the monitors that he'd got the shot he wanted, but I found it great working with him as the director. It calmed me right down. If I'd started with somebody else, I think it would have taken me longer to get where I got to.

Have you had to do any love scenes with him?

Yes, plenty of them. Because like every couple who meet and fall for one another, it's all kissing and sex for the first while.

I'm guessing it's not all scenes filled with scented candles and soft music?

Well, you know what? They kind of are, in a way, because from Libby's point of view it's incredibly romantic. Her boudoir, which we see in the first episode, is very romantic. I've rarely been asked to kiss somebody on stage or on screen for work at all. I found myself asking David on the first day "Do you go right or left when you're going in to kiss someone?" We didn't want to knock noses - and we're both very talented in that direction, we both have large noses.

And then filming a sex scene, I was really lucky that he was really comfortable with it, because it put me at ease a bit. But it's an odd experience, pretending to have sex with a strange man, and with another 17 people lighting your bottom and whatever else! And you don't want to frighten the audience with the wrong angles! So I'd never been asked to do sex scenes before, and we did the one where the kit was off. Because that annoys me, when you watch shows where you think "Why have they got their underwear still on? They've already had sex how many times?" So we did a nude one. It was possibly the least glamorous thing I've done in my whole life. It's just quite mechanical.

Was it quite terrifying beforehand?

It was. We were both being very brave about it. It was very short and very tastefully done, I have to say. Well, I haven't seen it yet, but I would say so, from where the camera was. And now it's done, and it was great, and I don't expect they'll ever ask me to do it again. But they might, and if you've done it once...

Hopefully you weren't quite as cold as you were today.

Although that would tighten the body beautifully! You'd be toned if you had that kind of cold around you.

Libby disappears for a while after the first episode?

Yes, something happens. The library is threatened with closure, and herself and Frank get into a bit of a situation because of that. And as a direct result, they are parted for a while. The course of true love never runs smooth. But they are eventually reunited.

Aside from the acting, you're also a successful writer. Are you writing at the moment?

I am. Oh Jesus. When I say that, what I mean is I'm supposed to be. Between series you have three or four months off. You would have thought that would be the ideal time for me to write, but no, I'm writing at the moment. I have the clash of all clashes going on just now. I don't seem to be able to do it any other way. I'm struggling with novel number eight at the moment, but I'm on the home stretch with it. It's quite weird, switching from one job to the other. Except I have quite often found that the job that you do, the people that you meet and the stories that they tell you, they'll feed in on some aspect of the writing. You'll think "That's a nice detail." Or even names. Certainly in the latest novel, there's a character called David, and there's one called Frank. And there's a Karen.

Maybe you'll have eagle-eyed fans going through the novel looking for references to Shameless.

For sure. Hopefully some University student will write a thesis about it. And nobody will understand a word of it. And if I'm ever asked, I'll say "Oh yes, that was all in there." Anything to look deeper.

We're afraid we have to bring up Mrs Doyle at this point...

Of course. Why not? How lucky am I? I got to be in two of the great Channel 4 series. If I were to die now, I would have had two bites at Channel 4's cherry. I can't believe my luck, to be honest. Mrs Doyle, and Ted and the others, are so beloved, and I think that's great. People ask if I get annoyed about still being associated with Mrs Doyle. Why would I get annoyed? People only mention it because they love it. Having said that, I'm delighted that in this Channel 4 show I get to play someone my own age. But what a great thing to have done. If I only ever put two things on a show reel, to explain to someone what I do, it would be those two roles. They're so different. Lots of people don't get a chance to experience any sort of variety at all- they get pigeon-holed in one part. It's so nice to be able to move on and do something different, and for that I shall be forever grateful to this wonderful show.

And back when you were playing Mrs Doyle, didn't you get presented with a British Comedy Award by Tony Blair?

I certainly did. It was 1996, he was just about to be elected Prime Minister. He also turned up at the South Bank Show Awards just after he'd been elected, and he was really nice. He remembered, and said "Ah, Pauline." I was bloody impressed. I'm sure he was very well-briefed. Who cares? It was impressive. It was very exciting, because around then was a defining time for him and for Labour - whatever you think about what's happened since. Me and Tony Blair. My part in his downfall. That's the title of my autobiography sorted.

And you're also learning Russian at the moment. What's that all about?

My lovely husband Richard has been learning it for a number of years, he's quite good now. And I made an idle remark one day about learning it as well, so we could talk to one another in Russian. He's grabbed that ball and run with it. He made me go to two hour lessons in a language school in Odessa recently, when I was supposed to be on a break. I went to school every day. Christmas Eve and Christmas Day, I did two hours of Russian lessons each day. And I had to walk through over three foot of snow every morning to get to my class!