How Lisa made the A-list

There are three things I know about Lisa Faulkner: first, that she's the one out of Holby City who always wore her hair, unadvisedly in my view, tucked behind her ears; second, that she's going out with Jonny Lee Miller. No, sorry, marrying Jonny Lee Miller, with a chic engagement ring - which, in turn, means living in North London and hanging out with Jude and Sadie. Third, she used to go out with Trey Parker, the malevolent genius behind South Park.

All these A-list chums, exes and fianc?s, combined with the fact that Faulkner shot to fame not even on an ambulance-chaser soap but on a spin-off, should add up to a woman who's punching way above her weight. While it's impossible to social-climb in our classless society, it is way possible to celebrity-climb from E-list to A-list, and the fact that Faulkner has pulled it off should, in theory, make her kind of grabby and monstrous. And more than that, she should look outlandishly pleased with herself, like a female Jefferson Hack with highlights.

None of this pans out - I arrive in the middle of the photoshoot, where the winsome 30-year-old is conducting herself with such affable courtesy that I assumed there was a TV camera lurking somewhere about (there wasn't). She told the photographer she was the best she'd ever worked with. And the make-up artist. And the stylist. She apologised to me because I was late (weird, no?). But if she disappointed by not being a bitch, that was nothing on how completely she failed to be a boiler. Actresses mainly let you down, looks-wise - the ones who look amazing on screen are all sinew and collarbone in real life and don't convey pure, dripping glamour so much as an all-over air of nerviness and snack-lust. Faulkner is dazzling - she looks so good, I swear, that the lame drunk-squaddie chat-up line - 'Did you hurt yourself when you fell from heaven' - would be a perfectly reasonable question. I was expecting a soap star with too much slap on, and I find a bona fide member of the aesthetic elite. This, obscurely, delights her: 'I was really pleased to have that frumpy look, because I'd gone from Brookside where I was playing this eyebrow-pierced rebel who was getting more and more toned down and prettier by the episode. And that doesn't interest me at all.'

Of course, she could be giving off some freakish post-engagement glow. She and Miller only got engaged a month ago, and there is still quite a bit of I-can't-believe-it's-not-butter excitement about the whole thing. Or, in her words, 'It was lovely. I'm thrilled. He just asked me to marry him, and I said yes. Lovely, yes, really lovely.' (Have you got that at the back?)

They've known one another since school and have been going out on and off since the end of 2000, and, well, she'd like to make clear the esteem she holds him in. 'I think he's wicked. He rocks.' Plus, all her friends are delighted, and her family, and the grandparents are the happiest of all. 'I think they thought I was going to be Bridget Jones. They're really thinking, "Thank God, she's finally got something right".' Bless. It's like Romeo and Juliet, without all the death.

Clearly, if you were marrying Jonny Lee Miller, the main problem would be that he was once married to Angelina Jolie, thereby consigning you to a lifelong hatred of someone who's going to crop up looking foxy all the time on billboards and the like. Faulkner doesn't seem in any way bothered about this. 'Oh, Jonny's been my friend for so long that I really don't think about it. I mean, I think she's the most beautiful woman in the world, sure, but God, it's in the past, isn't it? I don't really think about it. Life's too short.'

Faulkner is amazingly sanguine about what it's going to be like in a household with two actors. 'He's not a tantrumy actor at all. I mean, I think he has to put up with a lot. But he's very centred, he's very head-down-go-to-work, and he works out as well. So he's much more level, and I'm really up and down. But obviously something works.'

As for the wedding itself, the world clearly needs to know whether it's going to be in a Posh and Becks style, full of regal weirdness, or a Kate Winslet check-me-out-I-may-be-famous-but-I-still-like-sausage-and-mash affair. This question yields the only moment of caginess. 'I really don't know. We've discussed it. I just? Oh, I just don't know. Probably more along the lines of Kate Winslet.'

Don't mistake this for the joy of a person who just wanted to be married because she forgot it wasn't the Fifties. 'I wasn't really bothered, I've been much more "I want to work, I've got to work, I want to do something good".' That's why she's here today, to talk about her part in a new BBC drama about spies called Spooks. She plays a young secretary who wants to be a grown-up spy. Everyone else in it was really, really nice, and really, really good.

You hear this a lot from Faulkner - as a rule, she only wants to talk about other people. Amanda Redman, who trained her, is 'a brilliant, brilliant actress. I think she's absolutely beautiful and absolutely brilliant, and I think her career's wonderful as well. She's a total heroine of mine.' She'll stretch to an anecdote about herself only if it involves her sounding a bit dozy and wrong-headed. Like, say, when she met Jenny Agutter on the set of Spooks, having played her daughter in And the Beat Goes On six years ago: 'They introduced us, and she went, "Hi, nice to meet you," and I said, "You played my mum!" and she'd completely forgotten who I was. Afterwards, she came up and said, "I'm really sorry, you just looked so different," and of course it was fine, but I'd been all ready to have a real reunion, like she was my long-lost mum.' That said, her self-deprecation never gets in the way of her aspiration, like it would if it were genuine-article self-loathing.

She does aim high, she just keeps quiet about it. 'In England it's all "Who do you think you are?" if you start talking like that. Though you just have to live your life, don't you? People always go, "Why would you want to do this? What's the point of doing Chekhov?And it's because it excites me. Because deep down there's this frustrated actor/artist person. Sure, there's someone who likes to go to parties as well.' Hey, nobody liked a party more than Picasso.

The first step towards being an artist, of course, was to leave Holby City, which she'd been in for two and a half years. She'd made two best friends out of it, which pretty much compensates for all the shapeless green she had to wear. Angela Griffin (who's in the hairdressing yarn, Cutting It) and Nicola Stephenson are the ones she was always out with three years ago, when the tabloids were citing a new soap-based boyfriend for Faulkner every other week, and kept getting pictures of the Holby birds p****d in the back of cabs.

'We were three single girls going mad on the town, and we were suddenly invited to everything. And you're there with your two best mates, and you're getting free booze, and it's a real laugh. As long as you see it for what it is, and you're not constantly out, it's brilliant. But, yeah, the problem is that when you're single, whoever you leave the house with, that's who you're going out with, and before you know it, you've split up with them and you're going out with somebody else. I was always thinking, "How did I fit all these people in?"'

The giddy social whirl ended with a move to LA, to look for work and live with Trey Parker, which was even more fun, give or take the absence of a few core UK telly experiences. 'I mean, we went to a few parties, but I hate all that crap, I can do it for a bit, and then I'll go, "I really need to go to a pub. I need to eat mashed potato, and I need to watch Corrie and Blind Date, and I need to be happy".' (Note the connection between Blind Date and happiness. Cilla will be proud.) She came back for a part, but the whole South Park-moll deal was over as well, and everything went briefly sour.

'When I got back from LA, things were really tough, and not nice. And also, there's stuff in the press that really shouldn't bother you, but it does. And you know, without my friends, Jonny included, and my sister, I would have been really upset, it was a really down patch in my life.'

Faulkner claims to be ludicrously competitive about everything. 'I even get competitive about yoga - you know, relax and breathe, that's all there is to it. But you can't relax, breathe, and then look round thinking, "Is everyone else relaxing and breathing as well as me?'''

But for a competitive person, she's curiously comfortable talking about her failings, and she's very keen to point out how good other people are at her job - I don't think there's a single actress within a ten-year radius of her age that she doesn't say is wonderful at some point. 'I should really stop doing this, shouldn't I?' she says. 'I'm never going to get employed.'

She's currently unemployed until June, when she embarks on a mystery project that she can't mention in case she jinxes it. After that, she wants to do some more theatre: 'Sadie asked me to narrate it [the experimental Frost French fashion show], and it was the first time I'd been on stage for years. I was petrified, but the minute I got on stage and started talking, the buzz was incredible. And you can play with an audience, which you don't get to do in films.'

And in the meantime, she can just mess about. 'All my friends keep going, "God, how cool is your life at the moment?" and I go, "I know, it's brilliant, I'm really happy, and I've got a fantastic job to go on to, and a fantastic boy, and my family and friends and it's all?"' she rummages for the best possible word. 'Ner- ner-ner-ner-ner.'

Spooks is on BBC1 from 13 May at 9pm