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Warning - *major* spoilers for Line of Duty season five, episode four ahead.
Corbett, played by Stephen Graham, has been one of the main characters throughout season five after he was unveiled to be balaclava man.
It then emerged that Corbett was an undercover police officer working among some of the most dangerous criminals in order to expose police corruption - and unmask top corrupt copper 'H', just like AC12.
But things came to a grisly end for John during Sunday night's episode four of season five, as his throat was slit after he tried to leave the organisation of criminals.
The hardened criminals turned on Corbett after realising that he was still working with the police force, and lured him into a trap to kill him.
After his throat was slit, gang member Lisa McQueen (Rochenda Sandall) told him: "You're a rat John, a rat."
Corbett became the second major character to be killed off in this way in season four, as PC Maneet Bindra met the same horrific ending in episode two.
And at the end of season four, Assistant Chief Commissioner Hilton had his throat slit, as did Jackie Laverty way back in season one.
Viewers of Jed Mercurio's cop drama took to Twitter horrified by the gruesome scenes as Corbett lay bleeding at the end of the episode.
What is it with these guys and throat cutting?! #LineOfDuty... Oh and WTF?!?!? :astonished:
- Rob Rocklad (@london_rocklad) April 21, 2019
I can't deal with all the throat cutting. Oh and the terrible spelling. I don't know which one makes me feel most queasy #LineOfDuty
- Emily Allen (@allen_ems) April 21, 2019
Thought I'd got good at predicting #LineOfDuty but did not see that coming. They are loving a bit of throat slashing this series
- Joe (@Calvey94) April 21, 2019
"Well I felt they had Corbett pegged as the rat but I did not see that coming at the end... this series continues to thrill," exclaimed one fan.
Somebody else declared: "#LineofDuty did not see the throat cutting thing coming at all. So many twists."
"The throat slitting in this programme is brutal," tweeted a third.
And a fourth shared: "I gasped when Gina McKee had her throat slit in series 1. I gasped even more at the end of that episode!"
But we still don't know who 'H' is?!
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