The actor, who plays DI Steve Arnott, said episode four of the current series has the potential to be considered a “classic” among fans, describing it as “the big one”.
Posting a picture of Arnott aiming a gun in a tense-looking situation, he wrote on Twitter on Saturday morning: “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.”
HuffPost UK has seen the episode, and while we are not allowed to share details about what happens, we’d definitely agree with Martin’s assessment. We’ll be here to bring you all the latest analysis after the show airs on Sunday night too.
While all major spoilers are under lock and key, the BBC has shared a cryptic synopsis of the episode, which reveals there will be some “major breakthroughs” as AC-12 continue their investigation into Operation Lighthouse.
It reads: “DCI Jo Davidson faces increasing pressure from all sides as AC-12 make major breakthroughs in the investigation.
“Hastings acknowledges that the disciplinary action against him put Kate and Steve in a difficult position, and a forensic report from Farida’s house results in a shock for AC-12.”
Last Sunday’s episode saw corrupt police officer and OCG member Ryan Pilkington make an attempt on suspect Terry Boyle’s life by derailing a police escort and causing the car to crash into a lake.
Boyle has been framed by the OCG as the main suspect in the murder of journalist Gail Vella, who was investigating police corruption prior to her death.
Some fans also believed they spotted a major clue about the elusive “H” in the unlikeliest of places during the episode.
Line Of Duty continues on Sunday at 9pm on BBC One.