Line of Duty series 5 to explore the ramifications of Steve Arnott's balaclava man attack

The AC-12 detective was attacked by a balaclava man - of the criminal gang that has been at the heart of the action since the beginning of the show - in episode 3 of series 4, and it was suggested that he might never walk again. And though normal service seems to have been resumed in series 5, the actor has hinted that there is more to the story.

"As ever with [writer] Jed [Mercurio], everything is not quite as it seems. Steve has had the dramatic experience at the end of series four when he was in the wheelchair after being tossed down the stairs by Balaclava Man," he said. "At the start of the series, by all intents and purposes, he looks like he’s made a full recovery, but as we go through the episodes you start to realise it’s not quite right. There’s stuff wrong with him physically and that’s starting to affect him mentally and this will bleed into the current series.

"He’s a bit broken at times and the great thing about knowing that we’ve been commissioned for another series is that Jed can delve into characters' backstories more and, in this case, I think we see that Steve’s just a bit lonely."

And, Compston adds, there is a "certain problem" under the surface that is affecting his mental health, too.

"I’m not sure how much we can give away, but this series there is a certain problem that Steve has physically, which was a bit of an eye-opener when Jed told me about it," the actor said. "When you get down to the seriousness of it and how it affects him and his mental health, it turns out to be a very emotional scene."

Poor Steve...

Line of Duty series 5 airs Sundays on BBC1 at 9pm