The show follows AC-12, a fictional police squad assigned with uncovering corruption within the police force, and has previously starred the likes of Lennie James, Keeley Hawes and Craig Parkinson.
Here’s everything you need to know about series five.
Who’s in the cast?
Original stars Martin Compston, Vicky McClure and Adrian Dunbar all reprising their roles as Detective Sergeant Steve Arnott, Detective Sergeant Kate Fleming, and Superintendent Ted Hastings.
Maya Sondhi (Maneet Bindra), Polly Walker (Gill Biggeloe), Andrea Irvine (Roisin Hastings), Aiysha Hart (DS Sam Railston) and Tony Pitts (Lester Hargreaves) are also all set to return.
They’ll be joined by Stephen Graham who’ll play the nefarious Balaclava Man – the mysterious character at the centre of the fourth series, which also starred Thandie Newton and Jason Watkins.
What’s the plot?
The fifth series will shift focus from a single corrupt police officer to an entire “organised crime group”, led by Balaclava Man.
“That is the fresh ground that we break in the series,” Mercurio told Pilot TV magazine. “We’ve had these shadowy figures, ‘the Balaclava Men’, who are part of an organised crime group and have featured on and off all through the previous four seasons. But we’ve never really gone behind the mask and identified them as proper characters and found out about them.”
Is there a trailer?
A brief sneak peek of the fifth series was released after the finale of Bodyguard last year, revealing the return of AC-12, with Superindent Ted Hastings (Adrian Dunbar) is looking unhappy as he discussed the team’s next challenge.
This was followed up by an official trailer, which hinted that we’ll discover the identity of “H”, the corrupt cop at the top teased in the closing episode of series four.
Will there be more seasons?
Mercurio told The Independent that he wasn’t sure for how many seasons Line of Duty will run. “We all love making the show but I think a lot depends on how people respond to it,” he said. “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.”
When does it air?
The new series will kick off on Sunday, 31 March at 9pm on BBC One.