Martin Compston has revealed the helping hand he receives in nailing DI Steve Arnott’s accent on Line Of Duty. 

The actor hails from Greenock in Scotland but his long-running character speaks with an Estuary accent in the hit BBC cop show. 

Explaining he perfects Arnott’s accent on The Jonathan Ross Show, Martin revealed that someone actually records his lines for him to listen back to in order to help him get in character.

He said: “I walk about all day with him in my ears. It’s just graft.”

“I’m not naturally good at accents,” he continued. “I need to work harder, which then makes me better because I’m not complacent with it.

“If you’re in these scenes with these amazing actors, amazing guest stars, it’s intimidating enough without worrying about the accent. Speaking to the wife and stuff I’ll drop it, I very much stay in it (on set).”

Martin admitted the infamous interrogation scenes, which can be as long as 30 minutes and have to be filmed one full take at a time, are the hardest to keep up the accent for. 

He said: “It can be hard, that dialogue on its own would be hard anyway, throw the accent in there … the scene we did the other night, 30-pager, trying to juggle the accent at the same time.

“When we’re away from it for a long time, when I do that voice I can hear him, it’s like a costume.”

He also described DI Arnott as “the overdressed wanker in the call centre”, adding: “He’s the guy who is having all the office affairs and no-one knows how. He’s sort of unlikeable but he’s obsessed with his job and doing the right thing.”

Elsewhere in the interview, Martin also hinted Line Of Duty might not return after Sunday night’s series finale, saying that the “natural story arc that we’ve been on for the last six years” is coming to an end and the cast will not return “for the sake of it”.

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

AC-12 boss Superintendent Ted Hastings is among the suspects, along with DCS Patricia Carmichael, Chief Constable Philip Osborne, DI Kate Fleming and ex-officer Marcus Thurwell. 

The internet is already flooded with theories ahead of the finale, as many fans believe Marcus Thurwell is actually alive, after the character was found dead at his Spanish villa – and some of then claim to have the proof. 

Suspicions have also been raised about DCS Carmichael, as some viewers spotted what they believe might be a clue that confirms she’s “H”. 

The Jonathan Ross Show airs on Saturday at 9.35pm on ITV, while Line Of Duty concludes on Sunday at 9pm on BBC One.