The Scottish actor has to put on an Estuary English accent in the hit BBC drama.
The Dynasty legend was left wondering why it seemed like the Line Of Duty actor "wanted to kill her".
There was a surprise in store for viewers just eight minutes into Sunday night’s first episode.
The BBC's new thriller comes from the makers of Line Of Duty, and stars Suranne Jones and Martin Compston.
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.