Line Of Duty's Martin Compston promises upcoming episode 4 is 'one of the best' Jed Mercurio has ever written

The actor - who plays the recently promoted DI Steve Arnott in the police procedural - said the upcoming episode, which will air on BBC One on Sunday, 11th April, has the potential of becoming a "classic" episode in the show's nine year history.

Sharing a cryptic photo on Twitter of his character aiming a gun in the back of what looks like a police van, he wrote: "Tomorrow’s the big one episode 4! On paper one of the best @jed_mercurio has ever written, if we deliver what was there potential to be a classic.

"Like to give a shout out to the young team Shalom and @gregorypiper98 who give outstanding performances in the midst of the madness."

Shalom Brune-Franklin plays Ac-12's impressive new recruit Chloe, who fans are certain is the daughter of the late Tony Gates, who died in series one after getting caught up with the OCG following his illicit relationship with Jackie Laverty. Fans recalled that Gates had two daughters - Natalie and Chloe.

Gregory Piper plays Ryan Pilkington, who has been connected to the OCG since the tender age of 13 back in the first season, but is now an officer at Hillside Lane which is investigating the murder of Gail Vella.

Episode three featured Ryan killing a fellow officer, and attempting to murder Terry Boyle, who was being questioned in relation to the murder of journalist Vella.

Luckily, DI Kate Fleming (Vicky McClure) arrived just in time to intercept Ryan's evil plan. AC-12 has realised that Terry could have a story or two to tell about the OCG, after Ted Hastings (Adrian Dunbar) finally worked out that Terry's freezer was used to store Laverty's remains.

The drama has also seen Kelly Macdonald's, DCI Joanne Davidson, who heads up Operation Lighthouse, having links to the OCG after seemingly placing burner phones at the home of her ex-partner, Farida Jatri (Anneika Rose).

Meanwhile, Compston's Arnott has been struggling with back pain and an addiction to painkillers, and he's also abused his position of power by forming a romantic relationship with Steph Corbett, the wife of undercover copper John Corbett (Stephen Graham), who had his throat slit by Ryan in series five.

Former Line of Duty star Craig Parkinson recently suggested that Arnott could be the next major character to bite the dust during an episode of the Obsessed with… Line of Duty podcast.

Speaking about the ‘lies cost lives’ tagline which has been used to promote the series, Parkinson said: “Already, it’s scaring me. I feel something tragic is gonna happen to some character that we love.

“What the hell are we gonna do if something happens to Kate, Steve or Ted?” he added, before naming Steve as the character that he thinks could be offed next.

Line of Duty continues on Sundays at 9pm on BBC One. If you are up to date with the latest series, you can read our Line of Duty episode 4 recap here, or check out our theories on Jo Davidson's mystery relative. Take a look at the rest of our Drama coverage, or check out what else is on with our TV Guide.