Stephen Graham's undercover cop in Line Of Duty inspired by near-fatal bar brawl

The 45-year-old actor's father was struck with a knuckle duster and his wife, actress Hannah Walters, was left with massive scarring across her leg following the fight in Liverpool some years ago.

The This Is England star said he had drawn on the fear he felt then to recreate the anxiety and tension of being undercover in a criminal gang.

"I don't like to speculate. Did I have any part to play in it? I don't really think I did. There had been a disagreement, but I thought it was settled and left at a place of peace, a place of understanding.

"And then, when we left the pub, it just suddenly happened. My dad got hit with a knuckle-duster.

"Hannah has a huge scar on her leg. She actually dragged me away from the car that was going to run me over. So, I can draw upon that."

Corbett was killed off in the fourth episode of the latest series of the hit police drama, which ended on Sunday, with his throat being cut as he tried to quit the group he was undercover with.

Graham consulted an anonymous friend who served in Northern Ireland during The Troubles, who told him undercover agents "don't get second chances".

He said: "I did a lot of research with a friend who worked for the British Army back in the day and has to remain nameless.

"He used to be undercover in Northern Ireland, recruiting people for intelligence and information.

"What I learnt from him is that people working undercover don't get second chances. If he gets it wrong, then that's it. I tried to capture that danger in Line Of Duty."

The full interview is in this week's Radio Times.