Stephen's inside track on risky role
Line of Duty star Stephen Graham consulted an anonymous friend who served in Northern Ireland during The Troubles, who told him undercover agents "don't get second chances".
His character John 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 organised crime group he was undercover with.
He told the Radio Times: "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."
Sunday's finale scooped the biggest overnight rating of the year so far, the BBC said. The final episode peaked with 9.6 million viewers on Sunday night. It had an average of 9.1 million and a 44.1% share.