Line of Duty villain balaclava man has been linked to a number of grisly crimes since he first showed up in series four.
The identity of the masked criminal became a huge talking for viewers as he played a key role in some of the show's shadiest goings-on.
His most high-profile crime was the vicious attack on DC Steve Arnott.
In series four, Thandie Newton's character Roz was busy trying to frame others for the murder of Tim Ifield.
Arnott went to question her husband Nick Huntley, and after leaving his office a masked man appeared from nowhere and whacked him around the head with a baseball bat.
After a vicious struggle, the villain threw poor Steve over a banister and down three flights of stairs.
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Fans were convinced he was dead, but Steve managed to struggle back from the brink to make a full recovery - even if he was left in a wheelchair for sometime afterwards.
The attack fuelled speculation about who the man in the mask could be.
It wasn't the only incident he was said to have been involved in, as well as the shoot out at AC-12, he was also linked to the murder of Tommy Hunter, as well as a number of abductions and cover-ups.
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At the end of series four, it emerged that there were actually a number of different people operating as balaclava man, and one was killed in the shooting.
It was one of the numerous masked men who killed Basminder Kaur and Leonie Collersdale, abducted Hana Reznikova, and planted evidence in Michael Farmer’s home.
However, with the launch of series five producers let slip some more details about the main man behind the mask.
He's been named as John Corbett, a gangster and pivotal figure in a deadly organised crime group with links to corrupt police officers.
Corbett is being played by acclaimed actor Stephen Graham, best known for his roles in shows such as Save Me and Little Boy Blue .
Although not a super-villain himself, Corbett is believed to be under the direct command of the shadowy conspiracy kingpin known only as ‘H’.
He may be the key to unravelling the conspiracy of the last four series, which involved police moles from The Caddy - Matthew ‘Dot’ Cottan - and Chief Superintendent Hilton.
Line of Duty returns on Sunday 31st March 2019 at 9pm on BBC1.Do you have a story to sell? Get in touch with us at webcelebs@trinitymirror.com or call us direct 0207 29 33033.
