The fate of the show lies in the hands of writer and creator Jed Mercurio.
The Steve Arnott actor said he “fully understood” that the conclusion “wasn’t the 'urgent exit’ type ending some anticipated”.
Many fans believed the AC-3 boss is "the fourth man" after something Jimmy Lakewell was supposed to have said.
The Scottish actor plays English police officer DI Steve Arnott, and has admitted he's "not naturally good at accents".
Is this the end of the road for AC-12?
Line Of Duty Star Reveals The Very Stressful Reason Why The Cast Don’t Want To Mess Up Those Interrogation Scenes
And they sound every bit as intense to film as they are to watch.
We'd only just managed to calm ourselves down after Sunday night's thrilling ep.
We've uncovered all the secrets of AC-12 – because Hastings and co aren't the only detectives round here.
Martin Compston Proves There's Still Time For Fun On The Line Of Duty Set With Hilarious Vicky McClure Prank
The cast are currently filming the sixth series, after production resumed last month.
He plays D.S. Steve Arnott in the hit crime drama.