There’s a pleasing sense of unease that sits with you while watching Line of Duty. Pleasing, because it means that Jed Mercurio’s five-part drama is accomplishing the atmosphere it’s trying to create: an authentic world that bleeds further mistrust with every click of the mouse and every knock on a door.

It’s an excellent start to a series that promises much, coming as it does from the writer of Bodies and Cardiac Arrest. After a frenzied anti-terror raid gone wrong, DS Steve Arnott (Martin Compston) is the only officer who won’t cover up the fact that an innocent man was killed.

Ostracised, he transfers to Anti-Corruption Unit 12, where he’s set to investigate the unusually high conviction rates of DCI Tony Gates’ (Lennie James) department. Under close scrutiny, Gates has more than his job to lose, as he tries to cover up a supposed hit and run perpetrated by his mistress Jackie (Gina McKee).

From the taught and dynamic introduction to the slower, psychological chess that follows as AC-12 begins its investigation, the tension is so well sustained in Mercurio’s script that you’d be forgiven for being exhausted by the end of Episode 1.

You can feel it between every character as they circle one another, trying to sniff out the weaknesses and threats, unsure of the gravity of trust that binds them. This isn’t a gritty police drama, it’s a slimy one, and much like DS Arnott we’re drawn further and further into it and see the mistrust between its constituents.

There are strong performances from all, especially Adrian Dunbar as the ‘speak softly and carry a big stick’ Anti-Corruption officer Hastings, and Vicky McClure as DC Fleming, but it’s Lennie James who holds the entire hour – and likely the series – together in his depiction of corrupt DCI Tony Gates; a portrayal so compelling and complex that you start to get lost in it, as Gates’ choices become a dark moral labyrinth. ‘Laddering’ seems to be the least of his problems, as he covers up what increasingly looks to be premeditated murder by Jackie.

The reveal that Kate Fleming is working undercover for AC-12 doesn’t come across as surprising as it was perhaps meant to be, but it’s in what this will mean for Kate’s future, as she embeds deeper within Gates’ TO-20 blokes club, where the real excitement of the twist lies. That feeling of grim portent is strong across the whole episode as, much like the enormous dump Steve finds on his driver’s side seat, you’re not sure what dark deeds will occur next.

Almost certainly there’ll be worse acts to come than a strategically-placed shit before the series has finished. Based on Episode 1 we’re looking forward to see what they’ll be.

Aired at 9pm on Tuesday 26th June 2012 on BBC Two.

> Order Series 1 on DVD on Amazon.

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