Making The Bill look like In The Night Garden, Jed Mercurio has created one of the finest and most compelling police dramas of recent years. But it’s due to a uniformly strong cast, whose strengths have shown as the series has continued, that his gut-punch plotting and ‘spit & shit’ view of policing have succeeded.

Neil Morrissey in particular deserves special mention for playing the disgustingly loyal Morton, and Martin Compston and Vicky McClure both shone here, but it’s Lennie James who has carried the bulk of the drama, and his performance was at it’s most compelling as Tony Gates became his most desperate in a gripping final 15 minutes.

It’s been easy to forget, as we’ve been dragged down through dramatic morass of finger-choppings and murders, that Tony Gates has been a victim as much as he has been a perpetrator – forced into aggressively desperate situations by men far worse than he was. That helplessness was brought to fore in the final episode, as Arnott’s view of Gates in the grander scheme of things caused the audience to reassess our own view of him. Is Gates a good cop? No. Is he a bad man? Well…the line is blurred there, but that’s where the entertainment of this series has been created.

Even his death challenged our view of him; throwing himself under the truck just to see that his family would be taken care of, but also because he was mortally afraid of being a cop in prison (as had been hinted at several times across the series). Hero or coward? It was a death just as emotionally complex as his life.

Whatever your feelings about Gates, he wasn’t the cause of corruption, but a small symptom of it. DC Cottan’s shock affiliation with guttural golfer Tommy proved that TO-20 is broken, corrupt and, at it’s core, so cancerous that to fix it you’d have to demolish it completely. It was a reveal that made Tony’s death, all of Arnott and Fleming’s work, and even the glimmer of hope for boy-criminal Ryan, all the more hollow and bittersweet.

And on the theme of death, did we need to see (and hear) Sammy the dying dog be suffocated? It was unnecessary and unpleasant and, for being a needless indulgence in darkness, we can see it causing a stir among the Points of View crowd.

Doggy demise aside, this was an incredibly satisfying conclusion to a great summer drama. Not because it wrapped everything up neatly, but because it left much for us to consider. Though the core strands of the plot knotted together nicely, the wider injustices were left unsolved and undetected. A case for the audience to read between the closing lines.

It wasn’t clean, it wasn’t pleasant, but Line of Duty‘s final hour was a fitting end to a superb drama.

And if Mercurio ever fancies a return to the Line of Duty world, we’ll be back to watch quicker than shout an obscenity at a copper.

Aired at 9pm on Tuesday 24 July 2012 on BBC Two.

> Order Series 1 on DVD on Amazon.

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