If you thought things couldn’t get worse for DCI Tony Gates, then you’re right. As Line of Duty hits its halfway point they don’t get worse, they get catastrophic.

For the first two episodes Gates sat on his iron throne, fending off the barbs and jabs of the circling Anti-Corruption Unit with a smile or a growl. But now things have fallen apart. With Jackie dead (we’ll miss you, Gina McKee), and Gates being blackmailed by the drugs gang who killed her, he’s working harder and harder to come up with the next lie in order to cover up the latest in a long trail of them.

Lennie James plays the stress wrought on Tony beautifully, painfully, as his family and work lives begin to spiral away from his control and threaten to entangle themselves with one another. We feel his desperation and him rocking on the precipice of mental deterioration, but it’s impossible to empathise with him. This is a man who has chased the big crimes and played with the system for his own vanity, and his suffering is entirely self-inflicted.

Playing off this suffering, Neil Morrisey puts in a quietly impressive performance as stoic grey DC Morton, standing by Tony even as he begins to suspect that his hero and drinking buddy is not the shining copper he once thought.

After stalking around Gates for two episodes, DS Arnott finally takes a more offensive approach, as the passive-aggressive posturing between the two escalates into open hostility. It means that Martin Compston gets something to do beyond staring concernedly at a computer screen, and he does a thoroughly impressive job. The resulting questioning session between Arnott, Hastings and Gates was so tense and so blazing with unconcealed hate, you wouldn’t have been surprised if your screen had shattered right in front of you.

Occasionally things slip into a sensationalism that’s harder to swallow – did they have a freshly dead rat in the evidence locker or did someone from TO-20 hang around the bins with a truncheon and the ads section of the day’s paper to wrap it in? – and the drugs gang targeting Tony seems unusually organised (they’re even clearly on board with the government’s young apprentice scheme).

And do we really believe that Arnott has thrown in the towel? Do we heck. Even taking into account his conversation with one of his old Anti-Terror officers, it seemed more like a way to produce a cliffhanger for the episode than a natural progression. But in his (temporary) absence we’ll hopefully see the talented Vicky McClure given some more time to shine.

It’s almost a good job the summer nights have been such a washout lately. We can’t see the perpetual grimness of Line of Duty being palatable on a blazing sunny evening. But the weather’s terrible, so stay in, let the rain fall, and enjoy a rare treat of the summer schedules. Because, unlike the weather, this is a show that continues to impress.

Aired at 9pm on Tuesday 10 July 2012 on BBC Two.

> Order Series 1 on DVD on Amazon.

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