Anyone else watch the last moments of tonight’s Line of Duty through their fingers? We might have done. Be glad you still have those fingers. DS Arnott may soon not be so lucky…

It’s become apparent that, like a vindictive cinema manager, writer Jed Mercurio does not want you to flat out enjoy watching Line of Duty. He wants you to endure it, but gain enjoyment from that endurance. This was, in many ways, the darkest instalment of the series yet; challenging to watch in places but rewarding those who stuck with it with an hour of fine drama that’s all too rare in among the sport and yawns that form the summer schedules.

Only once did the show’s attempt at gritty miss the mark and became needlessly gruesome: did we really need to see Jackie’s jigsaw of a corpse being packed away like a bulk purchase of Iceland frozen meals being crammed into Kerry Katona’s freezer? It was a moment of unnecessary bluntness in an hour which had otherwise featured some nuanced emotion and impressive performances from the entire cast.

Arguably Line of Duty‘s strongest moments have been in its interviews scenes, as an increasingly confident Arnott and his boss Ted Hastings (Adrian Dunbar and his inscrutable ‘did I leave the iron on?’ eyebrows) spiral closer to nabbing their man. Once again the strengths of the cast emerge in these terse exchanges, allowing for some flesh to be put on the bones of Craig Parkinson’s DC Cottan, and for Neil Morrissey to continue to impress as DC Morton, a copper so loyal he’s practically handcuffed himself to the job. An ageing labrador of a friend, he limps beside Tony Gates even as he sees that his colleague’s career is on it’s last legs.

And as Gates is forced to make confessions all over the place; to his wife, to his team, to that angry Scotsman on the phone who’s rapidly becoming a Glaswegian version of The Claw from Inspector Gadget, Kate Fleming is on hand with false sympathy so convincing you almost be fooled to think some small part of her feels for him. It’s a subtle performance from Vicky McClure, who’s done exceedingly well with the little her character has been given, but then we’d expect nothing less from her.

Yet once again it’s the final few minutes of Line of Duty that give us the most to talk about, as Martin Compston’s DS Arnott is roused from a beating only to find himself mid-handshake with a vice. What followed was genuinely uncomfortable to watch, as vicious quick-cuts, the rising tension of the music, and off-camera screams kept us waiting on edge for the crackle of bone and the gush of blood.

What will Arnott’s fate be? We can’t see him losing more than one pinkie, but in a series this dark it wouldn’t be a complete surprise if he was killed either. Whatever happens to Arnott, Tony Gates is in so deep that his fate is sealed. We’ve endured the shockwaves of his corruption and his weaknesses, and now it’s time to enjoy seeing him get what’s coming to him. Because don’t think we’ve forgotten about the glass in the police station dishwasher…

Aired at 9pm on Tuesday 17 July 2012 on BBC Two.

> Order Series 1 on DVD on Amazon.

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