Kelly Macdonald says only the 'top Line of Duty cast' know who 'H' is

The Trainspotting star, who plays Acting Detective Superintendent Joanne Davidson in the sixth season, told PA news agency that only select cast members know the identity of 'H', a.k.a. the Fourth Man.

She said: "The main cast know. I don't know about everybody. H knows who H is... Like I said, I don't know the whole cast, but I know the top cast."

On the twist about her character's parentage, she added: "Jed Mercurio, man, he is troublesome. He keeps a lot to himself. I feel like Martin [Compston, her co-star] always heard about things first. I felt like he would get the lay of the land.

"I don't know if that was just because he is so on top of everything and understands everything acutely and what the connotations are.

"I didn't have the full story on Jo. I just knew that things hadn't been great for her. Jed kept saying, 'She is this enigmatic figure' and he was being enigmatic himself.

"By the time we came back after the first lockdown I knew what was up."

For more Line of Duty coverage, read our Line of Duty episode 6 recap, our ode to Carmichael and our explainer on Jo Davidson's 'father'.

Series six of Line of Duty concludes this Sunday night, 9pm on BBC One. To find out what else is on, or to decide on your viewing for tonight, check out our TV Guide or visit our Drama hub for all the latest news.