IF pubs and gyms had been allowed to open for the evening, or hairdressers to unlock their salons, the streets on Sunday night would still have been devoid of life. As 9pm approached, the four nations settled into a self-imposed lockdown, as they switched on for the latest series of Line of Duty. Briefly it felt like the 1970s, when you knew that everyone was watching the same show. The anticipation was so intense that phone calls in the preceding days ended not with “Stay Safe” but “Can’t wait for Sunday”.

Twelve months into the pandemic, there is almost nothing fresh to discuss. When speaking to one of my best friends, I find myself quizzing him about what he watched the previous evening. Twice a week he gives me edited highlights from the series he’s enjoying, but which we both know are too grisly for me. It’s like Jackanory with cadavers.

Texts from friends fly in with recommendations, and when neighbours pass there is a flurry of citizen reviewing covering the latest dramas to swim past our TV goggles. Much more pressing than whether Nicola Sturgeon would survive the political hyenas was gathering intel on the most recent crop of Walter Presents. People’s viewing tastes, I have discovered, are far more revealing than their DNA.

Of an evening, we scour Amazon Prime, Netflix and All4 like a forensic squad combing a spotless house for evidence. If you pass our window around 8pm, the chances are you’ll catch the sound of a barrel being scraped, as we set out in search of entertainment, like trawlermen dredging the seabed in the hope of catching something tasty.

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I don’t like to consider how many series we have begun and rejected, when the violence was excessive or the plot became too far-fetched. Yet that never dents our optimism as we embark on a new epic. Occasionally I’ll agree to something that is not propelled by crime – Call My Agent or The Terror – but nothing compares with the pleasure of sinking into a long-running story filled with red herrings, storylines entangled as cooked spaghetti, and preposterously dysfunctional sleuths. Best of all is knowing that when the series ends, the next will start in 18 seconds.

What is it about crime drama that is so addictive? Most viewers are law-abiding to a fault, with little worse than a parking ticket against their name. Finding a dead cat, let alone a washed-up body, would haunt us for days. Yet our hunger for imaginary homicide, preferably by psychopaths, seems fathomless. So too our tolerance for graphic autopsies, where heart and liver are weighed as casually as if they were stewing steak, and for scenes in morgues, with the obligatory big toe tagged like a Christmas present.

Were Police Scotland tasked with the case load of all the fictional killings that have taken place in their bailiwick, they would buckle under the strain. From Peter May and Stuart McBride in the north to Denise Mina, Chris Brookmyre and Ian Rankin in the central belt (the Borders where I live awaits its own fictional crime beat), writers vie with the Scandinavians for making us shudder.

The only thing they cannot offer, sadly, is a colloquial conversation class in another language. Val McDermid recently said that she has watched so much Scandi noir, she’s convinced she can now speak Norwegian. My unattainable dream is to watch Spiral or Le Bureau without subtitles.

Despite the thrill offered by the Parisian underbelly, for me it is the Coen brothers’ Fargo that stands above all others for its black humour and brilliance. Jed Mercurio’s clever script for Line of Duty, however, is the key to its success, allowing actors to fill out their parts rather than speak in cliches.

The Herald: Ian RankinIan Rankin

It is tempting to suggest that during these unsettling months we all need a figure such as Superintendent Ted Hastings to depend on. As played by Adrian Dunbar, he is a human Thames barrier, representing stability and protective strength as well as moral superiority. Yet long before the pandemic, he was the lynchpin of the show, the one around which all else revolved. You can’t trace the craze for crime drama to Covid 19 but to the way our brains are wired.

Line of Duty’s power lies in its sense of authenticity. It holds its own – and arguably surpasses – many productions from the US and Europe, who hitherto had claimed most of the plaudits. But its distinctive format is also a sign of how sophisticated crime aficionados have become. Interrogations in a dull office now offer the same thrill as courtroom dramas of old, but with none of the glamour of judges and dock, barristers and jury.

The psychology of cat and mouse, of the upholders of justice versus those wriggling under its telescope, lies at the core of our fascination. In this scenario, there’s no need for rhetorical flourishes or playing to the gallery.

The language in Line of Duty is prosaic and jargon-laden; the only props a tumbler of water and the steely gaze of inquisitor and accused. Therein lies the game for those of us at home, watching actors’ faces for a glimpse of the truth.

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And that, perhaps, is the clue to fictional crime’s enduring hold upon us. Everyone likes to think they’re a good judge of character, that we could spot a liar or a deadly threat at a hundred paces. From the safety of the sofa, we are reassured by believing we’re a step ahead of the detectives, and have a killer’s measure. Immersing ourselves in made-up crime in some way arms us for the everyday world, where we need to have our wits about us.

Seeing the depths of depravity and duplicity to which others can sink is a modern cautionary tale. Not just a wake-up call, it offers an enjoyable frisson of fear, and the comfort of seeing right prevail, and chaos averted.

Line of Duty, and all its kind, are the Grimm’s fairy stories of our benighted times. Like Little Red Riding Hood, Hansel & Gretel or Snow White, they open our eyes to dangers, real or imagined, that lie beyond our own doors. Or possibly within.

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