Click here to watch the Sarah Connor Chronicles trailer

Lena Headey has hit the big time. How big? The 34-year-old actress with the startling blue eyes and proud cheek- bones is big enough to carry entirely the new Terminator spin-off TV series The Sarah Connor Chronicles (she plays the title role). She's big enough to attract 18 million viewers in America to the opening episode. She's big enough to parlay a starring role in last year's beefcake blockbuster 300 into a heavyweight movie career (she's got four new films coming up, including Vivaldi, opposite Joe Fiennes, and the medieval thriller The Black Death). She is also, however, big enough to have both her agent and the director of studio marketing sitting within an oppressive hair's breadth of our table, scrutinising our increasingly fraught conversation.

Thing is, it didn't start out that bad. The Sarah Connor Chronicles is a giddy small-screen thrill ride loaded with camp pleasures that's sure to excite both franchise fans and casual viewers. The Yorkshire-born Headey thunders away handsomely throughout as the tough nut mother of Terminator-bait John Connor (Thomas Dekker). “No one is ever safe!” is a typical line, moodily hissed before a bulky humanoid killing machine devastates a school classroom. As such, you might expect an air of buoyancy about Headey today, or a sense of vindication that she has finally emerged into the glare of recognition after fitful trips through movies such as Face, Onegin and The Brothers Grimm, and TV such as The Gathering Storm and The Long Firm.

But no. Here at the corner table, back to back with agent and marketing honcho, there is hesitation and suspicion in her looks, and in our brittle exchanges. Her role as Sarah Connor, she explains drily, has been difficult for hardcore Terminator fans. “Crazy fans shout at me and say, ‘Linda Hamilton was great! You suck!'” she says, refusing to celebrate her sky-high professional status. “It's just a job, like any other job,” she says. “It comes with highs, but it also can be f***ing irritating. And it could be f***ing over tomorrow, so I don't get carried away. I've been doing it for 16 years.”

I tell her that it's funny, that I've been doing my job for roughly the same period, and that I've written five different “Lena Headey: The Next Big Thing” features, but that this time it seems, at last, like the real deal. She smiles, but she seems unduly hurt. There is a sharp intake of air from the agent's table. “See,” she says, “even you're exhausted by me. All I can say is that my job is like any job. It's like your job. I'm sure today you didn't go, ‘Brilliant! I can't wait to go down and interview her!'” She pauses momentarily, and adds, “Well, I feel the same way right now.”

There's a shudder of awkwardness between us. The marketing director stands up. “Last question,” he says, resting a hand on my shoulder, and prematurely ending our interview. This is a shame, I think, because I am, in fact, a fan. And Headey, born in Bermuda to a Yorkshire copper on a work exchange tour, and plucked at 17 from Shelley High School in Huddersfield to star opposite Jeremy Irons in Waterland, has a unique dramatic presence. Her screen demeanour can switch from delicate and willowy to full-beam intensity with a barely a twitch of her easily flushed features.

Of course, she has battled before, most famously with Terry Gilliam on the set of The Brothers Grimm - he wanted to cast Samantha Morton, the producers wanted Headey, and conflict ensued. But this is different. We can't end it like this. I ask the agent and the honcho if they could leave us alone, just for a while. Looks are exchanged, nods are given, and they do. “I feel like you're saying that I'm terrible at what I do,” she explains, once the coast is clear. “You are entitled to your opinion, but I'd rather you said I was f***ing awful to my face.” At this point I could mention the screen demeanour and the willowy intensity, but I tell her instead that I'm sorry, and that we should try to move on.

We talk, briefly, about her teenage years (she was depressed), about her love for British film (she is most proud of If Only and Imagine Me and You), and about her current interpersonal status - she lives in LA, in the Valley, with her husband of one year, the Irish non-actor and “real person”, Peter Paul. “I met him at a friend's wedding. I was the bridesmaid, and he was a guest, and now we're married and that's quite enough information for you.” She says that she's looking forward to kids, to family and to settling down, but that right now she's enjoying acting too.

She says that she's tired, and that she's slept for only two hours. Me too, I say. “Well, maybe we're both having a bad day,” she says. “It happens. And I know that I'm going to look back on this interview and what I'll think is that someone totally, totally, misunderstood who I am within the first ten minutes of meeting me.”

Ditto, I say.

She smiles. The agent and the marketing honcho reappear.

This interview, is terminated.

Terminator: The Sarah Connor Chronicles, Thur, Virgin 1, 10pm

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