Duty calls: Line of Duty's cast and creator discuss fourth series of hit police drama

Line of Duty returns to TV this Sunday night on its new home, BBC One. David Roy interrogated creator/writer/producer Jed Mercurio and cast members Martin Compston, Adrian Dunbar and Thandie Newton about what viewers can expect from the fourth series of the hit police-corruption-themed drama

DS Steve Arnott (Martin Compston), Superintendent Ted Hastings (Adrian Dunbar) and DS Kate Fleming (Vicky McClure) are back in Line of Duty

THE wait is almost over: Line of Duty returns for a fourth series next week in a new Sunday evening time slot.

The ratings-busting BBC Two hit, the channel's most-watched drama of the past 15 years, has also been promoted to BBC One for its fourth year, which sees guest star Thandie Newton (Westworld, Crash) joining the regular cast as DCI Roz Huntley, the latest 'person of interest' for police anti-corruption unit AC-12.

"My agent said to me: 'Thandie, an offer has come in and if you ever want to work in British television, this is it'," explains the London-born actress, who has been based in the US for the last few years.

"I've been with my agent since I was 17 so when she said something like that, I sat up. I didn't know anything about the role, but I said I wanted to do it."

Newton admits she had never seen Line of Duty before – but was soon hooked on the last series of the tension-packed show, which found AC-12 investigating rogue armed-response officer Sgt Daniel Waldron (Daniel Mays).

"I was completely knocked out by series three and Daniel Mays," she enthuses. "I’m such a fan of him, as with [previous guest stars] Keeley Hawes and Lennie James, I’ve admired them for years.

"They had clearly been attracted to the material and after meeting Jed [Mercurio], I was in."

DCI Huntley appears on AC-12's radar when doubts arise over an arrest during a high-profile murder investigation which she's in charge of: DS Steve Arnott (Martin Compston), newly promoted DS Kate Fleming (Vicky McClure) and Superintendent Ted Hastings (Adrian Dunbar) and their team are soon looking hard in her direction.

As ever, the exact details of the plot are being closely guarded by all involved.

"One of the things that has been so good about Line of Duty is that nobody wants to know what happens until they watch it," says Scottish star Martin Compston.

"Even my mates are like, 'Don't!' All I can really say about what to expect this time is that there's a whistle-blower situation and Thandie Newton's character is a new nemesis for AC-12 to deal with.

"We're chasing her down and it tos-and-fros, so it's very exciting. Thandie is a consummate professional – what was great was that she came in as a fan of the show, which is a testament to the success it's had."

A big part of Line of Duty's viewer appeal is undoubtedly the massive 'anything can happen' factor, something which means none of the cast members can ever feel too secure about what's going to happen to their character every time they get a new script for the award-winning show.

"Some of the later episodes aren't decided until quite late in the process," confirms Compston, who's been with the police drama since it began in 2012.

"But we have absolute faith in Jed: the scripts are first-class, that's the best thing about the show.

"So there's a bit of nervous excitement when you get the scripts to see where your character goes. But we know that anything Jed does is in the best interests of Line of Duty.

"He's a former RAF pilot and he was also a doctor, so he knows intimately about everything he writes about. He also does meticulous research to ensure every little detail is spot on. Whatever he writes and decides to do I'm happy to put total faith in him."

Co Fermanagh-born star Adrian Dunbar, another Line of Duty cast member who has been with the show since series one, advises fans that the latest season will bring plenty of unexpected twists and turns.

"Our viewers can expect quite a crazy ride," he enthuses. "The twists and turns are fabulous. Jed provides the audience with wonderful cliffhangers at the end of the episodes so you really are gripped.

"We're pushing the envelope again this year and people are going to be surprised in a different way. People who have stuck with the series from the beginning will be rewarded for doing so, and I think and hope that people will be as gripped as they've always been."

Indeed, Jed Mercurio admits he enjoys keeping viewers on tenderhooks throughout each six-episode run of Line of Duty.

"We hope once again to torment the nation with twists and turns," says the writer and series creator mischievously, going on to explain how crucial it is to cast a worthy antagonist for AC-12 each year.

"It's absolutely crucial to the synthesis of the character on the page and then the actor we’re lucky enough to get to play the role," says Mercurio. "That’s a process that starts at the script-writing stage, thinking who might be the right kind of actor and who might fill the shoes that we’ve created.

"We were incredibly fortunate this time with Thandie because we met and there was really very little in the way of discussion. We met and it was something that felt right straight away.

"We went through the same process for the previous three series – it’s just so important to the identity of each one, and we probably do position that antagonist role as our defining feature."

Another key character in Line of Duty is its regular 'home' in Belfast, which plays an un-named English city on-screen.

Even after five years with the show, Greenock-born, LA-based Martin Compston says that he still looks forward to working in Northern Ireland and enthuses about the local hospitality shown to him by cast-mate Adrian Dunbar.

"Aidy knows everyone and he's so proud of where he's from," he tells me. "He's a great guide for us because he loves Belfast. He's really keen to show the place off so he's always taking us to gigs, shows and different restaurants.

"I'm very lucky to have him and Vicky McClure to share the experience with. I genuinely love getting over to Belfast for the filming – it's something I really look forward to. It's a fantastic city and being from the west coast of Scotland means the people are very familiar to me.

"We're there for four months at a time so it's like doing a film. We stay in town so it means we can get out and see a lot of the city. I love Mourne Seafood and The Spaniard is my favourite bar – it's a cracking wee place.

"I'd love to get out more and see others bits of Northern Ireland. I'm dying to do the Giant's Causeway so I'm going to try and get that one ticked off."

Perhaps he can persuade Mercurio to take Line of Duty up the coast for a few episodes next year – assuming he'll still be with the hit BBC show, of course?

Compston laughs: "I'll be here until Jed decides to kill me off!"

:: Line of Duty starts on Sunday March 26 on BBC One at 9pm.

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