It was the size of the sky that first captivated me. In the British television adaptation of Henning Mankell’s Wallander detective novels, the horizon always seemed somehow lower than it should be. Most of the time, at least two-thirds of the screen was slate grey, or steely blue, or else a deep black stippled with stars. Kenneth Branagh played Mankell’s tortured Swedish detective, his face working hard in the gaps of the sparse script, brooding with his back to all that sky.

This was just the start. Once Branagh’s Wallander had been devoured, there was still the Swedish adaptation of Mankell’s novels to enjoy, and then suddenly I was watching more television with English subtitles than without. The Killing, Borgen, Arne Dahl, The Protectors, The Bridge – Scandinavian television became the reason we stayed at home on Saturday nights.

The “Nordic noir” phenomenon, as it has become known, is no longer confined to the small screen. On 1 and 2 February, a former brewery in east London played host to Nordicana, “the UK’s only festival of Nordic fiction and film”. Thousands packed into a chilly, windowless warehouse space to see actors and writers from the various shows try to account for their wild popularity beyond their intended audience in Scandinavia.

Sidse Babett Knudsen, who plays Birgitte Nyborg, the lead in the Danish political drama Borgen, clearly has ambiguous feelings about the way the role has changed her life. “I know it’s really what rock stars say, but I do ‘love my fans’,” she jokes – but then seems a little less sure of this once the “fans” at Nordicana start asking her such questions as: “Which are better in bed, English or Danish men?”, or spending minutes enthusing about her in broken, hesitant Danish. Not all Nordic noir fans are just enthralled by the skyscapes.

Do these dramas deserve their critical success, though? Or do we enjoy them merely because the subtitles lend a smug feeling of superiority? Some of the performances – by Knudsen in Borgen, say, or Sofia Helin as the abrupt, inspired detective Saga Noren in The Bridge – are undoubtedly excellent, but awkward dialogue and improbable plots are perhaps less noticeable here than they would be otherwise. Everything about them – the landscapes, the interiors, the languages – has kindled a love affair with a version of these countries that may not exist.

We think of Scandinavia as a progressive utopia where gender equality rules politics and there are minimalist lamps in every house. But according to Michael Booth, the author of a new book, The Almost Nearly Perfect People: the Truth About the Nordic Miracle, our vision bears little relation to reality. “Once you go beyond the western media’s current Scandinavian tropes … a more complex, often darker, occasionally quite troubling picture begins to emerge.”

Yet even though Booth’s research into levels of taxation and reliance on antidepressants has a much stronger grasp of reality, it will make little difference to our adoration. It is exactly the same kind of comfortable cognitive dissonance that makes Downton Abbey such a success in the US – of course American viewers can tell it’s camp and ridiculous and poorly scripted, but investing in the belief that the British aristocracy was just like this is far too enjoyable for us to stop watching.

We love our imaginary Nordic paradise too much to abandon it now – the jumpers are cosy, the sky is vast, and its television is very, very good.