Line Of Duty star Martin Compston has shot down one of the theories fans have about the identity of “H”. 

Many viewers of the hit BBC cop show believe DCS Patricia Carmichael might be “the fourth man” after a line of dialogue Jimmy Lakewell apparently said. 

Some people on Twitter claim Lakewell told Martin’s character DI Steve Arnott to “look beyond the race claim to find H”. 

It’s thought to be a clue because if you take the letters R A C E C L A I M out of Carmichael, you are left with one letter, H.

However, during an appearance on The Jonathan Ross Show on Saturday, Martin explained why we’ve all got it wrong. 

He said: “Do you know what I love about that one? It’s so spot on, but that line never got said… blew my mind.

“Jed [Mercurio, the show’s writer and creator] said, ‘No, that line never happened.’” 

Of course, that doesn’t necessarily mean that Carmichael – played by Anna Maxwell Martin – isn’t “the fourth man”. 

During last Sunday’s episode, viewers picked up on the fact Carmichael tapped her pen four times during DCI Jo Davidson’s interrogation scene, which is Morse code for ‘H’. 

Addressing the theory on The Jonathan Ross Show, Martin’s co-star Vicky McClure, who plays DI Kate Fleming, would not be drawn into commenting. 

“Hmm that’s very interesting, yeah.,” she said. “Very, very interesting…”. 

Anna tried to brush off the speculation when she made an appearance on This Morning earlier this week. 

When hosts Holly Willoughby and Phillip Schofield presented her with the video evidence, she said: “I think I was just bored. Those scenes are very long. I think I was like, ‘What am I saying next?’”

A trailer for Sunday’s series finale has promised viewers that the identity of ‘the fourth man’ – otherwise known as ‘H’ – will be revealed during the episode. 

Carmichael is among the suspects, along with Superintendent Ted Hastings, Chief Constable Philip Osborne, DI Kate Fleming and ex-officer Marcus Thurwell. 

Line Of Duty concludes on Sunday at 9pm on BBC One.