SCARCELY has the “hysteria” - Jed Mercurio’s own word - over his wildly popular drama series, Bodyguard, died down than excitement is stirring over another of his creations.

It was announced today that filming of the fifth series of Line of Duty, about the work of the police anti-corruption unit, AC-12, is underway in Belfast. Stephen Graham, whose CV includes Save Me, Taboo, and This Is England, will star as guest lead, ‘Balaclava Man’.

“It’s gonna be explosive!” was the prediction of one of the drama’s lead stars, Scots-born Martin Compston, who plays DS Steve Arnott.

“I’m absolutely delighted to be back with the AC-12 family, brought together once again by the phenomenal scripts of Jed Mercurio.

“A huge part of the show’s success over the years is the incredible guest stars we’ve had and this year is no different. It’s an absolute joy to be working with Stephen Graham again - someone I’ve always looked up to as an actor. He’s a brilliant addition to the Line Of Duty team.”

The BBC confirmed that Graham will play John Corbett alongside Rochenda Sandall as Lisa McQueen.

Corbett and McQueen play “two pivotal figures in a deadly organised crime group. Known to have links with corrupt police officers and suspected to be under direct command of the shadowy figure known only as ‘H’, Corbett and McQueen become persons of interest to AC-12 following an explosive chain of events.”

Graham and Sandall, who featured in Girlfriends, and Broken, will join Compston and the other regular leads - Vicky McClure (DS Kate Fleming) and Adrian Dunbar (Supt. Ted Hastings),

Graham said it was an “honour” to have been asked to join the Line Of Duty team. “I’m especially looking forward to working with Martin Compston and Vicky McClure again,” he added.

Sandall said she was “honoured to be working with such a talented team of people, and to be working side-by-side with Stephen Graham, who I have watched and admired onscreen since I was young.”

Vicky McClure praised the “fantastic response” from the Line Of Duty audience and said it felt “extra special” to be back filming series 5.

“I absolutely love working with Martin and Adrian, and Jed has without a doubt stepped it all up a gear this series,” she said.

“His writing just gets better and better. We have lots of great new cast members and I’m over the moon Stephen is on board, he’s a good friend and one of the finest actors. I’m already excited for the twists and turns to hit the screens.”

Adrian Dunbar, meanwhile, said: “Every time we open the scripts and every time Jed does it again. It’s great to be back with my Belfast family, even if the children appear to be a little wayward…”

The fourth series of Line of Duty was the BAFTA-nominated crime drama’s most successful yet, airing for the first time on BBC One where it attracted an average audience of 8.2 million viewers. The series’s four finale was the programme’s highest rated ever, with a consolidated figure of 9.9 million viewers, placing it among the top five dramas of 2017 across all UK channels.

Bodyguard, which was created and written by Mercurio, and starred Keeley Hawes as a Home Secretary and Richard Madden as her protection officer, David Budd, was the BBC’s most-watched drama since 2008.

Its audience reached a peak of 11 million in its final five minutes.

“After the hysteria surrounding Bodyguard,” Mercurio said, “it’s a relief to be back in the day job. I’m delighted to be working with the old gang and welcoming our brilliant newcomers led by Stephen Graham and Rochenda Sandall.”

The new case for AC-12 will be set nearly two years on from the previous instalment.

Piers Wenger, Controller of BBC Drama, said Mercurio’s scripts had again “attracted an outstanding cast to Line Of Duty, and its stellar performances and bravura storytelling will once again ensure that the series is unmissable, event TV. It is tremendously exciting to be working with Jed and the World Productions team again, as filming for series 5 is now underway in Belfast.”

The new series will see the return of Maya Sondhi as PC Maneet Bindra, Polly Walker as Gill Biggeloe, Aiysha Hart as DS Sam Railston, Tony Pitts as Det. Ch. Supt. Les Hargreaves and Andrea Irvine as Roisin Hastings.

They will be joined by Line Of Duty newcomers Taj Atwal (In The Club, Stella), Richard Pepple (Motherland, Beasts of No Nation) as new regulars PC Tatleen Sohota and PS Kyle Ferringham, alongside Susan Vidler (Shetland, The Coroner), Sian Reese-Williams (Hidden, Requiem), Ace Bhatti (Bohemian Rhapsody, No Offence) and Elizabeth Rider (Informer, Doctor Foster).

Simon Heath, CEO & Creative Director of World Productions, which makes Line of Duty, said Stephen Graham was joining the “best-loved cast on British television for another thrilling instalment” of Line Of Duty.

The fifth series will be screened on BBC One next year.