Line of Duty, Series 2, BBC Two

Crikey. Line of Duty was pumping dangerous levels of octane first time round. For this new series we’re in for an overdose. After one hour the body count is racking up: 3 coppers (shot), 1 witness under protection (burned to a crisp), AN Other (defenestrated). Plus that lovely soft Keeley Hawes has been waterboarded in the lav and has assaulted a noisy neighbour with a wine bottle.

Series creator Jed Mercurio is proud to deliver a cop show that cops don’t have to watch with curled toes. They may not like what they see – their own criminal behaviour being investigated by colleagues in Anti-Corruption – but no one can quibble on the details. Mercurio knows how the police wear their hats and fill out forms and conduct interviews. The only difference is that this is drama, so even the deputy chief constable is pretty and the script is on amphetamines.

Mercurio knows just as much as any Scandy about the foxtrot pulse of crime drama

The first series told of a star detective (played by Lennie James) who went on the take to fund a lifestyle far beyond the limits of his salary. We are superficially in similar territory – a policewoman is suspected of lining her pockets, only this time round the motive would seem to be desperation. DI Lindsay Denton is single, unpopular and up to her armpits in debt with an elderly mother’s care to fund. An apparently blameless pencil-pusher, she is the only survivor of a drive-by shooting when a witness under protection is moved from a secure location. As she was the officer in charge, her colleagues smell a rat: hence the dunking she takes in the loo. But is Denton actually at fault? The beady-eyed regulars of AC-12 are called in to work out if the killers were indeed acting on an inside tip-off.

We know they're good at what they do, and there's lashings of procedural to prove it. But this time round, rather than focus remorselessly on the hunt for criminal coppers, Mercurio has also chosen to peer into the lives of his main protagonists. Thus Adrian Dunbar’s avuncular Irish superintendent Ted Hastings is in the throes of a marital breakdown and poker-faced DC Kate Fleming (Vicky McClure) is having a ding-dong with the husband of one of the murdered officers (nul points for plausibility). That leaves Martin Compston’s frowning cockney DS Steve Arnott, who is soon out on the town flirting with pouty newbie DC Georgia Trotman (Jessica Raine). And who wouldn’t? Trotman is empathetic in the interview room and knows all too well how to neck a lager. This is just a hunch, but there may not be much future in their liaison. (Pictured above right, Martin Compston and Adrian Dunbar.)

We are all fixated on how they bring psychotic baddies to book in those ice-cool locations up near the Arctic Circle. Line of Duty keeps its feet more squarely on the ground than The Bridge. There are no swanky landscape shots as the camera cuts and thrusts and wobbles around a faceless city centre without much ceremony. But Mercurio knows just as much as any Scandy about the foxtrot pulse of crime drama: the slow slow sifting for evidence; the quick-quick power surges of plot acceleration. And the acting is unflashily on the money – Hawes without a stitch of mascara has never been more compelling.

If every episode ends with quite such an upheaval as this first one, it’s not a seatbelt you’ll need, but a parachute.