Line of Duty theories: Steve Arnott is withholding key info from Ted Hastings after episode 4

Possible off-screen moment could become important in future episode

Line of Duty viewers believe a cryptic moment in episode four has teased a future Steve Arnott revelation.

The latest instalment of the BBC drama’s sixth series was shown on Sunday (11 April), and stunned fans with its many twists and turns, including one, quite literally, relating to DCI Joanne Davidson (Kelly Macdonald).

*Spoilers follow – you have been warned*

Its tensest moment, though, arrived midway through the episode during a sequence in which DI Arnott (Martin Compston) attempts to extract key information from prisoner Jimmy Lakewell (Patrick Baladi) in the back of a bulletproof van amid a police convoy.

However, proving that the OCG has informants working in the prison, the convoy is ambushed by gunmen who opens fire on the van. Arnott and Lakewell are seen stuck in the back together with police backup on the way.

After making it out alive, Arnott heads back to AC-12 where he interviews Lakewell alongside Superintendant Ted Hastings (Adrian Dunbar) and DC Chloe Bishop (Shalom Brune-Franklin).

Does DI Steve Arnott (Martin Compston) know more than he’s letting on in ‘Line of Duty’? (BBC iPlayer)

They vow to place him on a witness protection programme should he give up the name of the corrupt officer at “the top”.

However, Lakewell says he’d rather take his chances back in prison, where he believes he’s relatively protected.

“You can really imagine you’ll be safe in prison,” Arnott asks, to which Lakewell says: “They’ll know I didn’t talk, so yes, I hope so.”

He then adds, after a pause: “That’s right, isn’t it, DI Arnott? I didn’t talk.”

It’s here where Hastings leaves the room and, after another pause, Arnott cryptically nods at Lakewell.

This could mean that Lakewell gave up key information to Arnott while they were stuck in the back of the van – but that he wrote it down, which is why he emphasised the point that he “didn’t talk”.

If this is the case, the fact that Lakewell was garrotted when he returned to prison means that Arnott may now know something revelatory that he’s holding back from both Hastings and Bishop.

Line of Duty continues on BBC One on Sunday (18 April) at 9pm.