Line of Duty star Stephen Graham reveals “none” of the cast know who the final 'H' is

“I’m being deadly serious – none of us know.”

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Graham’s vengeful cop Corbett had his throat cut in episode four, making him the latest big-name actor to be slain by writer Jed Mercurio, who’s become notorious for killing off characters played by Lennie James, Jessica Raine, Danny Mays, Keeley Hawes, Craig Parkinson and Jason Watkins in past series of the show.

And it turns out Graham and Mays, whose character was shot dead in the first episode of series three, have been having a laugh about both being killed off by Mercurio.

“While Line of Duty’s been on air I've actually been doing a new comedy for Sky with Danny Mays called Code 404, in which we both play two policeman,” said Graham.

“So it was great, Danny came in after the first episode and he was like, 'Mate, I thought it was great, you were fantastic. You lasted longer than me anyway!'”

Graham also revealed that he knew he would be playing the mysterious balaclava man from the end of series four – “quite a while before it got announced” – and that he actually really liked wearing the face mask when filming in cold conditions in Belfast.

“It was quite comfortable actually, especially in those weather conditions in Northern Ireland, yeah, it was great.”

Line of Duty is as known for its complicated plot as it is for AC-12's long interrogation scenes, and Graham admitted that he would often have to read the script multiple times to get a handle on what was going on.

“You have to read them and read them and read them. Me, Martin, Vicky and Adrian would sit down and we'd go through it and go, ‘Right, okay, so that's going on there and that's going on there.’

“But with Jed, he's such a wealth of knowledge on the whole subject, and we created a whole backstory for the character that I play.”

Graham will next be seen in The Virtues on Channel 4. The series – written by Shane Meadows and Jack Thorne – centres around Joseph who, struggling to recover from his addiction to alcohol, sets off for the south of Ireland to confront repressed memories from his childhood years in care and to reconnect with his long lost sister Anna.

The series – which also stars Helen Behan, Frank Laverty and Niamh Algar – begins on Wednesday 15th May at 9pm.