Her crusading reporter Katrine Fonsmark in Borgen is ambitious, hardworking, exercises too much, eats too little. "Which is certainly not the case for me," says Birgitte Hjort Sørensen
Birgitte Hjort Sørensen is already sitting in a booth at the back of a Japanese restaurant when I arrive for our lunch in Mayfair. It was her choice of venue and I'd assumed it was because sushi is the preferred diet of calorie-conscious actresses on perpetual detox.
But I notice Sørensen, 31, already has a glass of champagne in front of her and a twinkle in her eye. Another glass is immediately produced by a solicitous waiter. We clink and each take a swig.
It rapidly becomes clear that we are going to get along.
Within a few minutes, the Danish actress has told me that she loves London, because "I like the structure – I like knowing that you have to stand on the right side of the escalator," and that she feels "a sort of kindred spirit with journalists" as a result of her most famous television role.
Sørensen plays the crusading reporter Katrine Fonsmark in Borgen, one of the biggest dramatic hits set in Denmark since Hamlet. The series follows the life of the country's fictional first female prime minister, Birgitte Nyborg, as she negotiates the difficulties of coalition both in government and in her marriage.
British audiences have responded in droves to the obvious parallels of coalition politics but arguably what makes Borgen so riveting is its effortless script and intricate subplots. Each episode focuses not just on the main power players, but also on the ambitious backbenchers, spin doctors and idealistic journalists who attempt to mould the story to their own ends.
Whereas The Killing was all moody brilliance and dark murderous undercurrents, Borgen is lighter in tone and broader in scope. Yet, underpinning both dramas is a determination to show life as it really is – with all the attendant messy personal relationships, complex characters and 2am Chinese takeaways.
The first two series of Borgen attracted more than a million viewers and scooped a Bafta. Little wonder, then, that the third and final series has fans whipped up into a frenzy of anticipation. Why does Sørensen think Borgen, which started out as a small-scale foreign language programme airing in the twilight zone on BBC4, proved so popular in the UK?
"I was quite surprised," she admits. "It seems to me that you've really taken to the strong female leads and being a working mum. It's my understanding that maternity or paternity leave is more difficult here than at home … Quite a lot of British women stop working when they have children and that is rarely the case in Denmark. We have a very flat, structured way of approaching everything. Nobody's the boss. In a sense, we're all equal."
This is actually how Sørensen speaks: Her sentences are constructed like intricate pieces of crochet, the words slotted into place in English that sounds as if it has been lifted from the pages of a period drama. When she orders an avocado and sashimi salad, she does so with all the precision of Dame Judi Dench measuring up a bonnet for the Cranford village fete. Her spoken English was shaped by a childhood diet of gentle English television – she remembers loving Poirot and Miss Marple.
Her fondness for quintessentially British drama has stayed with her. In June she appeared in a feature-length Marple alongside Julia McKenzie. Later this year she will be starring in the 100th episode of Midsomer Murders, a joint production with a Danish TV company, called The Killings of Copenhagen. She's even taking on Shakespeare: in December, she's returning to London to play opposite Tom Hiddleston in Coriolanus at the Donmar.
Before Borgen, she was used to getting character descriptions outlining the necessary attributes as "cute, beautiful, sexy, whatever…" She flaps her hand, swatting away the idea with distaste.
For Katrine Fonsmark, by contrast, the character description was "ambitious, hardworking, exercises too much, eats too little…" Sørensen breaks off and laughs. "Which is certainly not the case for me."
In Borgen, Fonsmark is ethical to the point of extreme stubbornness – scathing of other people's weakness, determined to communicate the true story rather than the lines being spun by those in power. As a journalist, I confess that watching her is both invigorating and rather intimidating.
"The thing with drama is you're allowed to invent people who are maybe slightly better than real people," Sørensen says, kindly. So is she more adept at compromise than her character? She nods. "I do believe you should have principles but it's easier to survive in the long run if you're flexible, in order to not be completely alone in the world."
Much of the fizzing sexual tension of the first two series of Borgen was provided by Fonsmark's on-off relationship with the prime minister's spin doctor, Kasper Juul, played by Pilou Asbæk. The two actors went to the same drama college; Asbæk was in the year below. "He actually played my father once in a student production of Don Juan," Sørensen recalls. "Which was a little odd."
On screen, they have an obvious chemistry. Which is why, when I get sent the synopsis of the final series of Borgen, I am devastated to learn that the couple have split up and Fonsmark is now a single mother, struggling to balance her work and home life.
But do the two characters still get on as friends? I ask pathetically.
"Yes," Sørensen says, practically patting my hand. "They do." She has the grace to look sympathetic.
In another context, she would have had an excellent bedside manner, and for a while medicine was almost a career option. Sørensen's parents are both doctors – her mother works in geriatrics while her father is an ear, nose and throat specialist. She grew up in Copenhagen with two older sisters and, at the age of 14, had a work placement on her mother's geriatric ward. But she found the experience dispiriting. "For weeks I was with all these people who used to be able to take care of themselves but who were now old and no longer able to wash or feed themselves," she says. "It was so depressing."
When she talked to her mother about it, "her reaction was: 'It's good that we can help', whereas I felt I lived too much with their sadness. That was the difference between us."
Back at school, she began to do more theatre and went on to study at the Danish National School of Theatre. After graduating, she found work almost immediately. She has "a soft spot" for musical theatre and, in 2008, did a 10-week stint in London as Roxie Hart in the West End production of Chicago.
Midway through a mouthful of tuna sashimi, I confess I struggle to see her as, well… "A musical actress?" she interjects, stretching out her fingertips and doing a Liza Minnelli-esque approximation of jazz hands.
"I don't think of myself as a musical actress… but I think the good thing about Roxie Hart is that she's a wannabe, so even if your leg doesn't come up to here" – she signals with her chopsticks to a point halfway up the wall – "it's OK."
Now that Borgen has come to an end, she's looking forward to getting back on stage. "It's more rewarding … You are in control. In film or TV work you can have this amazingly dramatic pause and they'll just edit it out."
As a result, Sørensen says she doesn't particularly like watching herself on screen and compares it to the embarrassment of listening to your own voice on a tape recording. When Borgen aired in Denmark, the only way she could deal with it was by inviting a group of close friends around each week to watch it with her.
"It takes a little getting used to," she says. "Vanity aside, it's also about me remembering: 'Oh, that was that take where this happened and I was a bit distracted'."
She takes a final mouthful of her salad. We finish off the champagne and settle the bill. As I get up to leave, Sørensen stands and shakes my hand formally. She tells me not to worry too much about the fact that Kasper and Katrine are no longer together.
"It will work out," she insists.
Like I said – she has an excellent bedside manner.
Borgen is on BBC4, Saturday evenings; the DVD box set follows on 16 December