Line of Duty cast interview: ‘The first thing you do with the script is check you’re not dead’

Actor Adrian Dunbar is recalling walking down the street in north London recently when a police car came shooting past with its blue lights flashing. “They saw me, screeched to a halt, rolled down the window and shouted ‘Oi! Line of Duty!’”, says Dunbar, who plays Superintendent Ted Hastings in the BBC1 saga about police corruption – a subject that might not automatically endear the series to the constabulary. “I think the police like it because we are so procedural and we are so correct,” he adds.

By “we” Dunbar means creator and writer Jed Mercurio and his ex-police advisers who anchor the heart-pounding show (whose fifth series begins on Sunday 31 March) in a realism that often might mean, for example, that the cast are asked to learn lines consisting entirely of police acronyms. Martin Compston, the Glaswegian actor who speaks with a light cockney accent as DS Steve Arnott, often bears the brunt of this jargon.

“There was a line I had that contained five acronyms in one sentence,” he says. “Absolute torture but somehow they’re thrilling. The show’s been really brave in things like that from series one and I think we were incredibly lucky to start out on BBC2 where we could really find our identity before we went to a bigger audience.”

The first series of Line of Duty, which tells of the fictional police anti-corruption unit AC-12, went out in June 2012, becoming BBC2’s best-performing drama of the preceding 10 years. Series two added to this audience and, in 2014 the channel commissioned two further series back to back. The fourth and most recent series was promoted to BBC1, attracting an audience of nearly 10 million to its climactic episode in April 2017. That may have been dwarfed by the final episode of last autumn’s Bodyguard, which lured 17 million viewers, but the fact is, of course, that Bodyguard and Line of Duty share the same writer, Jed Mercurio. He’s obviously doing something right.

A Lancashire-born former doctor and Royal Air Force officer, Mercurio turned to TV writing in 1994 with his blackly humorous BBC2 hospital drama Cardiac Arrest, which would later be voted the most realistic medical drama of all time by a panel of health professionals. The 52-year-old has become a master of edge-of-seat plotting, which he describes as “finding a balance between the plausible and the unexpected”.

The unexpected often involves killing off a major character early on in a series. Jessica Raine’s Georgia Trotman, having been introduced as a new member of AC-12 and a love interest for Steve Arnott, was famously thrown out of a window at the end of the first episode of series two, while an early exit also awaited Daniel Mays, whose corrupt officer Danny Waldron was abruptly terminated in series three after his actions dominated the opening 50 minutes. And in the most recent series, history appeared to be repeating itself when Thandie Newton’s Roz Huntley ended the first episode unconscious and apparently about to be dismembered by Jason Watkins’s psychopathic forensics bod. She survived that, albeit losing an arm in the process, but it was a clever sucker punch by the puppet-master Mercurio.

So, what can fans expect from the new series? Since it features in the trailer, it would be no spoiler to say that it all begins with the hijacking of a police convoy that leads to three deaths (echoes of series two here, when a police convoy is similarly ambushed). It also wouldn’t be news that Stephen Graham (This Is England, Boardwalk Empire) is playing the guest criminal, John Corbett, part of a deadly, organised crime group that has links with corrupt officers and is suspected of being under the direct command of the shadowy figure known only as “H” (more on “H” later).

Graham is reliably menacing, his casting a reunion with Vicky McClure, who plays the other AC-12 regular DS Kate Fleming. Both actors got their big breaks in Shane Meadows’s 2006 film This Is England. “I’ve worked with Stephen a lot and he’s one of my best mates,” says McClure. “But the minute I heard he was coming on this I thought, ‘God, we’re all going to have to pull our socks up again.’ He’s a powerhouse... you see that from the minute he steps on screen.”

There’s a classic Line of Duty reveal towards the end of the episode, which, without going into details, brought to my mind Conrad’s Heart of Darkness. Whether or not any of the characters will face an early death in the new series, I’ve been asked not to (and wouldn’t anyway) reveal, but the threat of a premature demise stalks all the characters, however longstanding. “The first thing you do is check that you’re not dead,” says Dunbar of receiving fresh scripts.

Mercurio only gives his actors three episodes to read at the start of every six-part series, which Adrian Dunbar says helps keep his acting fresh and in the moment. “You’re not making decisions based on some arc of where you know you’re going to end,” he says. “So, everything’s really immediate which keeps it very alive in terms of filming it.”

“It’s very much in the present tense, everything feels now,” says executive producer Simon Heath. “It’s never written with hindsight and never acted with hindsight. Nothing signposts you to what’s going to happen next and I think people love that. He lays trails.”

The biggest trail of all is the one leading to the identity of the corrupt police mastermind known simply as “H”. ACC Derek Hilton (played by Paul Higgins) appeared to point the finger at Hastings before seeming to identify himself by committing suicide after his own corrupt past was exposed. Dunbar is naturally reticent about whether Hastings is indeed “H”, but given the covert glances shared by Fleming and Arnott, they obviously have their doubts about their boss, while McClure says fans have their own wild theories. “One invented a middle name for me, Helen, and suggested that I might be ‘H’,” she says.

And then there’s the identity of Balaclava Man (or Men), one of whom put Arnott temporarily in a wheelchair. Mercurio adds that the actors themselves help him keep on top of the countless, potentially confusing story threads. “The cast are really helpful in remembering things,” he says. “We actually kick around a lot of ideas together, and we might start thinking about a loose end from previous series – that was interesting, is there anything we can do with it?”

With the sixth series already commissioned, the big question is how long Mercurio can continue with Line of Duty. “I don’t know,” he says. “We all love making the show but I think a lot depends on how people respond to it. It’s great when people get very excited about it and they get to the end of the series and they’re talking about what they want to know and what they want to see next.”

Dunbar adds that although fans are desperate for answers, they also want to avoid spoilers. “You’d imagine that the public would want to find out but actually, the reality is that people come up and say, ‘we really love the show but don’t tell me anything’. People like to watch it in the moment, as it goes out live… and I think they like to know everyone else is watching it at the same time and they’re all going through these moments together.”

Line of Duty season five begins on Sunday 31 March on BBC1 at 9pm