Line of Duty series 5: The definitive guide to who’s who in AC-12

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Anna Brech
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Vicky McClure, Adrian Dunbar and Martin Compston in the TV drama series Line of Duty

As Jed Mercurio’s gripping cop thriller returns to our screens this season, a reminder of who’s who in Line of Duty series 5

After an agonising two-year wait, BBC show-stopper Line of Duty is back on our screens this month, with its trademark grit and pace. 

Jed Mercurio’s hard-hitting drama takes us inside the murky world of AC-12, the controversial anti-corruption unit that keeps tabs on other officers in Central Police. 

Series 5 of the hit thriller opened in true style last week, with a tense and gripping ambush scene. A police convoy carrying a £100m stash of heroin came under fire in a country lane, leaving three officers dead and another mysteriously spared. 

Cue: secrets, lies and enough grisly gratuity to rival your average Scandi noir. 

In a world where no-one is whom they seem, and plot twists come quicker than you can shout “noooo!”, here’s a quick recap of everyone you need to know:

Lead badass: DI Kate Fleming

Kate Fleming played by Vicky McClure in the TV drama series Line of Duty
Kate Fleming played by Vicky McClure in the TV drama series Line of Duty

Hard-nosed investigator Kate Fleming will stop at nothing in her quest to root out the truth. A stalwart fixture of AC-12, her dogged determination and unshakeable moral compass has seen her rise up the ranks in recent years. 

Series 5 picks up as the DI emerge from another undercover stint. Does she have what it takes to stomach the latest round of drugs, death and intrigue at play in Central Police? We have 100% faith.

Unsung talent: Reeling off acronyms at a dizzying rate. OCG, UCO, ED905, ACDC (OK, maybe not that last one) – Fleming keeps us all on our toes with her spitball knowledge of police jargon.

Played by: Vicky McClure

Maverick cop: DS Steve Arnott

Steve Arnott played by Martin Compston in the TV drama series Line of Duty

You won’t get so much as a grin out of the grimly determined Detective Sergeant Steve Arnott. But then you wouldn’t smile much either, if you were forever putting your life and soul on the line to hunt down bent coppers (and wow, there are a LOT of them). 

Series 5 sees Arnott continue his recovery from a previous run-in with “Balaclava Man”, with a glimpse of pill-popping that may hint at an addiction problem. 

Unsung talent: Going rogue. A little bit of rule-breaking is in Steve’s DNA, and this tendency has landed him an impressive roster of injuries in the past. But hey, what’s a mangled digit or two when you’re bringing down the bad guys?

Played by: Martin Compston 

Old timer: Supt. Ted Hastings

Ted Hastings played by Adrian Dunbar in the TV drama series Line of Duty

Superintendent Ted Hastings heads up the AC-12 unit, with all the sombre commitment of a boss who’s been around too long. Fastidious about his way of doing things, Hastings is not everyone’s cup of tea. 

In fact, his scruples and a recent run-in over sexism have cast a major shadow of doubt over where his character really lies. 

Unsung talent: Being slightly unfathomable. Sometimes Hastings comes across as a kindly paternal figure, and on other occasions, his behaviour really grates. Don’t assume you know him too soon. 

Played by: Adrian Dunbar

Wild card criminal 1: John Corbett

John Corbett played by Stephen Graham in the TV drama series Line of Duty
Stephen Graham as John Corbett 

It wouldn’t be Line of Duty without a suitably sinister gangster and this series, the honour appears to goes to newbie cast member John Corbett. We say appears, because of course, nothing is quite as it seems where Mercurio’s twisty plot tactics are concerned. 

At first glance, Corbett is placed as the kingpin in this series’ Organised Crime Unit (OCU); one of the deadly “balaclava gang” who tormented AC-12 in the previous season. 

Unsung talent: Being slippery. Like any bona fide baddie, Corbett is simmering with aggression and menace. But what’s his real agenda here? Only time will tell. 

Played by: Stephen Graham

Wild card criminal 2: Lisa McQueen

Lisa McQueen played by Rochenda Sandall in the TV drama series Line of Duty

Lisa McQueen is John Corbett’s criminal sidekick and subordinate; a key figure in the OCU lot. She says she was recruited into the criminal underworld as a teen, trading drugs across county lines.

McQueen keeps her cards close to her chest but seems to be more cautious and less ruthless than her blood-lusting boss. Or is it just that she’s more calculating?

Unsung talent: Empathy. A criminal with a conscience is more intriguing than one without. Early on in series 5, McQueen displays a capacity for mercy that is glaringly at odds with her gangster colleagues.

Played by: Rochenda Sandall

The big mystery: informer “H”

Martin Compston, Vicky McClure, Adrian Dunbar and Stephen Graham in TV drama series Line of Duty

Of all slippery figures in Line of Duty, the elusive “H” is the hardest nut to crack. “H” denotes the top dog in command of the organised crime; he or she known to be a senior officer, with direct links to corrupt cops. 

Some people (*cough* Supt Hastings *cough*) believe this mystery ended with the apparent suicide death of Chief Constable Derek Hilton in series 4. Hilton had long been affiliated with organised crime, and his cover was eventually busted. 

But Fleming and others have doubts that Hilton is the only, or even the right, undercover officer who operated in the balaclava gang. 

Unsung talent: The ability to stir up some seriously dark office politics. This unknown player puts your average water cooler spat into the shade with his or her ability to spread suspicion and abject fear in the workplace. 

Played by: Who only knows…

Images: BBC Pictures 


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Anna Brech

Anna Brech is a freelance journalist and former editor for Her six-year stint on the site saw her develop a vociferous appetite for live Analytics, feminist opinion and good-quality gin in roughly equal measure. She enjoys writing across all areas of women’s lifestyle content but has a soft spot for books and escapist travel content.