Morven Christie: "I think it's kind of heartbreaking that women have never seen a reflection of themselves in film or on television."

There's my intro, I tell her. Christie laughs and continues: "Actors are doing this a lot now, a lot more than they used to. They're almost branding themselves. I don't want to do that. I'm not really interested in being an 'actor'. I'm interested in acting."

You know the face, right? Perhaps you remember Christie from ITV drama Lost In Austen, or maybe BBC Olympic sitcom 2012? She also turned up in Doctor Who. She's the beautiful heiress in comfy sofa detective series Grantchester. And soon, you will have the chance to see her up close in The Driver's Seat, a National Theatre of Scotland adaptation of Muriel Sparks's bleak, disturbing novel, and Christie's first ever proper appearance on a Scottish stage as a professional actor.

It's the end of the week in a Glasgow cafe. Earlyish. In an hour, Christie will head off to rehearsals for The Driver's Seat, but for now she's talking. Though not about Unicef. It's possible that's the only subject she doesn't discuss this morning. Politics, Shakespeare, social media, sexism, all get an airing. There's even a story about Dennis Hopper chain-rolling joints and teaching her about method acting while on the set of a terrible film you won't have heard of.

In short, Christie is your perfect interviewee: sparky and outspoken and someone who answers all my questions. The only thing she doesn't want to talk about is whether she is still married to film director Scott Graham.

The Driver's Seat is a disturbing tale of male violence and female loss of identity. Christie is halfway through rehearsals when we meet. "How's it looking? I have no idea. It's so different from anything I've done before."

The play, directed by NTS artistic director Laurie Sansom, is going to be a heavily designed multi-media thing, it seems. "It's not the kind of theatre I've ever done before," says Christie. "I've always done quite naturalistic stuff. So, yeah, it's a bit of a change."

She's also still finding her way to her character, Lise, the woman at the dark heart of the play and Sparks's novel. "Yeah, she's in a pretty dark place. Her behaviour is very extreme. Even before it begins she's a person who has been pushed to her limit of living so it's not a comfortable skin to wear every day."

Christie, it should be noted, is happy to call herself a method actor. It's how she was trained in London's Drama Centre. "The kind of actor I am, I start in the middle and work my way out. Some start with the outer and fill in. The behaviour, the physicality, outer things. I go the other way. I go to the bits of myself that I identify with and layer on the other stuff."

But what if the character has no centre? What if the character is impossible to pin down? As is the case with Lise, a character who is seen through the eyes of others, someone who puts on a different mask for everyone she meets. "I read this play and went, 'Oh my God, who the hell is this person? That's really scary and I don't know if that's going to work and I don't know if I can do it. But I won't die. I'll give it a try.'"

Lise, she reckons, is profoundly lonely. And that's a way in. "What happens if you take that one time that you felt lonely and magnify it and keep going with that until it fills your entire being?"

So what was the moment in your life that you felt so lonely, Morven? "I think I was really lonely at school. I didn't go very much. I hated it. It's maybe part of being an actor - not that I was an actor then - of kind of sitting on the outside of things, observing. And so never feeling part of things. School was definitely like that. And because it was like that I didn't go very much. I spent a lot of my time in my house by myself and my parents didn't know I was there."

She'd sit at home watching telly, writing, drawing. Hiding behind the sofa when the truancy officers came calling. There must have been letters. "There were. It got pretty bad. They threatened not to let me take my exams, but my grades were so good. For some reason I didn't find schoolwork challenging.

"They did call my parents up to the school but it had taken them so long to notice that my parents were absolutely furious. The point they got in touch with my mum I had 87 absences that term and my parents' question was - 'How did it take you so long to notice this?'"

This would have been in Glasgow. Christie was born in Helensburgh and grew up in the city with her parents and her older brother. Holidays were spent in Aviemore. Your parents were French, I say. There's a look of disbelief on her face. They weren't? "Wikipedia's a killer. Somebody sent me a text. 'Here, are your parents French?' 'No.' 'It says they are on Wikipedia. 'They're both from Aberdeenshire. No Frenchness.'"

Let's rewind to Aviemore. Christie could ski from the age of four or five. "We were up there regardless of the season. In the summer we climbed hills and in the winter we went skiing if the weather allowed. That was very much part of my childhood, part of my teens and my early adulthood. I taught for a while and I raced as a kid. That was much more my community than school was."

Christie's parents met at youth theatre. Dad was an actor, then a drama teacher, all before she was born, then a lighting director. She would sit in the lighting box with him on show nights.

Yet she never did drama growing up herself. After school - if that term applies in her case - she started working in shops and restaurants and on the ski slopes. She travelled for a while, came back, moved to Edinburgh and started a communications course at Telford College. As part of it she had to do a small drama piece. It made her realise that's what she should be doing. She worked up an audition piece and started applying to drama schools. Drama Centre in King's Cross, London, was the one she set her heart on "because the prospectus terrified me. They said this thing about how you needed to live it, breathe it, eat it, sleep it. It was extreme. I wanted that".

It plunged her straight into method. As a result she's not always been happy in English theatre. "I think there's an English style of theatre that's quite head-based. It's quite an intellectual, academic society. But none of those plays were written to be academic. They were written all about feelings. People don't write plays about intellectual ideas. When I did Romeo And Juliet the director specifically cast me because I wasn't that. But there's definitely been other Shakespeare productions where it was, 'OK, this is all very high-brow and intelligent and we can talk about the iambic pentameter.' But who really cares? What about the feeling? The oomph?"

How do you spell "oomph"? "I don't know," she laughs. "It's the gut. The reason all those plays have endured is because the humanity in them hasn't changed in hundreds of years. That's why they live now."

Christie spent the best part of 15 years in London after drama school but last year she moved back to Glasgow. Though she loves it now, she hadn't missed the city in all that time. "I missed the Highlands," she says. "I missed that perspective it gives you: the ability to stand, look out at a big sky and go, 'It doesn't really matter. You're tiny.'

"And through the referendum campaign, that grew and I had this visceral longing for the land. So I moved back. I set myself this deadline of being here in time to be on the electoral register in time to be able to vote. It was not the referendum that drew me home, but it started a process that was already waiting to wake up."

Ah yes, the independence referendum. Anyone who was following Christie's Twitter feed during the campaign was in little doubt how she was going to vote. "Me and Twitter, I should stay off it. I forget that most of the people who probably follow me are fans of Grantchester, which is a nice little show about a vicar in Cambridgeshire."

During the referendum campaign Christie even got into a bit of a Twitterspat with the English actor Frances Barber, who had been outspoken against the Yes campaign. Have they ever met?

"Yes. I did a radio play with Frances Barber." It's clear they're not close. "Throughout the referendum I saw a lot of stuff on her Twitter about Scots and the SNP." Well indeed. At one point, later deleted, Barber condemned the SNP as reminiscent of the Third Reich. Christie wasn't impressed. "You're not talking about an idea. You're talking about my family, my friends and me. That's not true. It's xenophobic and really aggressive and I'm not going to ignore this. I think it hit me so personally.

"A lot of actors use Twitter only for professional stuff. I don't have that element to my personality. I'll go, 'Oh here, by the way, I'm in this play. Anyway, politics ...' I'm just not good at that s***."

Thing is, she's always been this outspoken. As soon as she had left drama school, she was complaining about the lack of roles for women. The week before we talk, Maggie Gyllenhaal revealed that she was told she was too old at 37 to play the lover of a 55-year-old actor. Does that suggest the industry is institutionally sexist? "I think it is," says Christie. "Hollywood has a massive issue with this. Americans do not believe a woman can lead a film. They just don't believe people will watch it. Maybe they won't in America.

"Fundamentally the problem has been for a very long time, most of the writers are male and when you write you write from your own experience. It's logical."

There need to be more women writers, directors and commissioners, she says. "It's not the industry part that bothers me. It's the assumption that an audience isn't interested in women and 51 per cent of that audience are women. It's kind of heartbreaking that women have never seen a reflection of themselves in film or on television, whereas every type of man, every age group of man, their story has been told.

"And you realise that with young female characters - and by young I mean under 30 - they're always a sort of sexual fantasy of the male writer. So if they fancy Kate Moss at her grungiest and not Megan Fox at her glammiest it's still a sexual fantasy. I have to fit that picture of what's attractive. Male characters don't. It's frustrating."

Christie is in her mid-30s now. Presumably it's getting even harder. "Definitely, yeah. There's just nothing around."

The answer, she says, is to take control. "Because I've found there are fewer avenues to put myself into, I've been writing. So the answer, I think, is for women to write stories."

She wants to direct, too. She's even written a script. "We'll see how difficult it is for me to get it made."

It's almost time to go. But first, I bring out a picture: a Vanity Fair shoot of Shakespearean actors from 2006. Christie is lolling at Judi Dench's feet in a gossamer dress between Patrick Stewart and Ian McKellen. She was rehearsing for Romeo and Juliet. How does she feel about the picture now? "I remember the experience of that day, which I hated. What does it make me feel? I don't know. It doesn't look like me."

The magazine gave her a framed copy, which she kept in the bathroom of her tiny Tottenham flat. "Me and Judi in the bathroom. When I moved I thought, 'What am I going to do with this? I don't want this.' I don't know what it makes me feel."

You don't feel plugged into that world? "Nah. I don't feel that this world really ..." She trails off.

What? Exists? "Yeah. And that whole Shakespearean actor thing ... It's not a world I want to be plugged into. Judi Dench is fantastic. Ian McKellen is wonderful. But the actors that I admire are not in that picture. The actors I admire are Marion Cotillard, Juliette Binoche. Frances McDormand. It's not my world. It's just not my world."

Morven Christie is an actor. That's actor with a small A.

The Driver's Seat opens at the Royal Lyceum Theatre, Edinburgh, on Friday and runs until June 27. It then transfers to Tramway, Glasgow, from July 2 to July 4