A decade ago the unthinkable happened: a subtitled TV drama about people agreeing with one another went global. On paper it bore the hallmark of a barrel-scraping pitch from Alan Partridge. Somewhere between youth hostelling with Chris Eubank and monkey tennis, he might easily have proposed a new ne plus ultra in implausible entertainment concepts: Danish coalition politics.

Yet Borgencaught a thermal and soared. The show took its name (which, correctly pronounced, sounds like a Cockney saying ‘Bolton’) from the so-called fortress in the heart of Copenhagen where state business is conducted. It featured Birgitte Nyborg, a moderate heroine who snuck into Denmark’s highest office through a small centrist crack between left and right. Embodied by Sidse Babett Knudsen, whose background was all in comedy, there was steel in her eye and sandpaper in her voice – but that gigawatt smile of hers could melt a thousand icecaps.

Perhaps unconsciously groomed by Borgen, before the second series aired Danes elected their first ever non-fictional female statsminister. Helle Thorning-Schmidt, professing herself a fan, compounded international interest in the show. Though France was the earliest adopter, the UK was soon rapt as BBC Four pumped out episodes in pairs of a Saturday night. It helped that, for the first time in for ever, we too were experiencing the befuddling Euro-hybrid of coalition government. The cross-party cabinet was said to include students of Borgen.

We’d all been softened up for it by The Killing, the viral whodunnit from Danish state broadcaster DR which had political subplots hardwired in. But in lieu of Nordic noir, this was Nordic nice. Borgen’s stars (the ones who weren’t already known from The Killing) became familiar faces. Babett Knudsen, an impeccable English speaker, made two movies with Tom Hanks. Birgitte Hjort Sorensen (who played news anchor Katrine Fonsmark) and Pilou Asbæk (spin doctor Kasper Juul) both popped up in Game of Thrones.

DR almost never commissions a third series of anything, but Borgen was a cash cow projecting soft power and so Nyborg, out of office and newly divorced, formed a new party and electioneered her way back to her spiritual home, now as foreign minister. And that was apparently that. After 30 episodes currently bingeable on BBC iPlayer, audiences were left to imagine Nyborg exporting her moreish brand of Scandi consensus around the planet in perpetuity.

And yet here are Sidse Babett Knudsen and showrunner Adam Price on my screen explaining why Borgen has returned.

‘We said to each other back then,’ says Price, ‘that if the right story came along we would try to bring it back at some point in the future. It’s just the sort of thing you say at a wrap party.’ Babett Knudsen pipes up: ‘And I said, “We’ll talk about it again in ten years.” I lived very well without Borgen. I was doing fine and then Adam came and said: “I have the story. It wasn’t really intended for the Borgenuniverse, but do you think maybe we should move it there?”’

In those ten years Price, who in Denmark has a side hustle as a celebrity TV chef, was slated to form a scriptwriting power couple with Michael Dobbs, creator of House of Cards. Their collaboration didn’t bear fruit. Perhaps elements of it have resurfaced in the new Borgen’s thrillerish plot, which topically enfolds fossil fuels and global warming, Russian badassery and arm-wrestling between the US and China.

Some of the story is set in post-colonial Greenland, which, lest we forget, Donald Trump once tried to buy. More pertinently still, in Mette Frederiksen, Denmark now has its second female statsminister. So does Borgen. When it was broadcast in Denmark earlier this year, viewers spotted that power-hungry new PM Signe Kragh is somewhat modelled on Frederiksen, speaking with the same accent, being adept at Instagram and a devotee of canned mackerel. These and other contemporary matters arising from the series – from Twitter trolling to green activism – were all food for thought as politicians, reporters and Borgen stars discussed each episode on a special weekly edition of DK’s Det Politiske Talkshow.

I ask Babett Knudsen if she has ever met either of her factual equivalents. ‘No,’ she says. ‘It is completely deliberate. To me it’s just super-essential that I have to stay within the world of Borgen to believe in it, which is also why, when we’re shooting, I can’t watch the news.’

Instead it’s Price who’s been glued to the headlines, even seeming to foretell them. The first episode, which alludes to aggression against Ukraine, was launched in Denmark four days before Russia’s invasion. ‘Actually Birgitte is referring to the Crimean war in 2014,’ he says. ‘It just sounds as if it has just been written. That’s just the terrible chance of fate.’

Reinstalled as foreign minister, it’s Nyborg’s task to swim with the superpowers while fighting her corner in the coalition and quashing unrest in her own party. At home she also wrangles with her son Magnus, once a little blond cherub but now a strapping and querulous eco-warrior. (The rest of the returning cast look ten years craggier.)

Otherwise her personal life is a void. Blessedly there is no sign of the colourless British starchitect she dated in the third series. I ask what happened to him. ‘Terrible terrible tragedy,’ deadpans Babett Knudsen. ‘He got run over by a bicycle and you don’t think of these things as being dangerous but bicycles are, like, really really dangerous in Copenhagen. He was so young and so fit. And we had great sex until the end.’ She then slips in and out of the first person. ‘It’s always been a secret little dark wish that one day I will be able to devote myself completely to my work. Birgitte experiences this as freedom. She thinks she is having her time of life. But the camera is showing something different.’

A trigger warning for fans of Birgitte Nyborg’s pragmatic idealism: it’s weirdly upsetting to witness her moral disintegration across eight episodes. Price cites Lincoln’s bon mot that served as the epigraph for a previous episode: ‘Nearly all men can stand adversity, but if you want to test a man’s character, give him power.’ Not for nothing, along with a new signature tune and a new home on Netflix, is there a portentous new title: Borgen – Power & Glory.

The international takeaway from Borgen was that the Danes are just much nicer than the rest of us. But this series portrays realpolitik red in tooth and claw. I ask Price if we haven’t misread the national psyche?

‘I don’t think you have. I think we are quite nice. We don’t believe that the system is rotten and we very much believe in our democracy and that is a core value to Birgitte Nyborg as well.’ As he lionises his fictional heroine, the woman who plays her plants a loving kiss on his cheek. ‘Ooh yes,’ he says, ‘keep doing that.’ Now that they’re back, will they keep doing Borgen? ‘The possibility is there,’ is all he’ll say.

We need Nyborg. In the real world, it has taken war in Europe to throw up a political leader that the West can agree to admire. Before Volodymyr Zelensky became president, he played one, which must be somewhere in the back of my mind when I ask Sidse Babett Knudsen if Birgitte Nyborg can be relied upon to save the world. She pauses for thought, unleashes that gold-medal smile and says: ‘Of course.’