It is one of the most watched programmes on BBC iPlayer, and Line of Duty is back.
The show, along with its gripping storyline, is known for its guest stars and Kelly Macdonald has been confirmed as the latest to join the cast.
The new season is sure to follow on from the previous drama, twists and turns of season five - this is what we know so far.
Who will star in Line of Duty season 6?
The team of AC-12 will all return to screens for season six. The leading duo of Line of Duty, Kate Fleming (Vicky McClure) and Steve Arnott (Martin Compston), have both confirmed they will be returning for the latest season, along with their boss Ted Hastings (Adrian Dunbar).
New faces include Prasanna Puwanarajah (Doctor Foster), Andi Osho (Kiri), Perry Fitzpatrick (I Am Nicola) and Shalom Brune-Franklin (Our Girl).
However, the most exciting new face will be Kelly Macdonald, playing DCI Joanna Davidson.
Her character will be the lead detective on an unsolved murder, which requires the help of AC-12, but she will prove difficult to manage as she takes an unconventional approach to her investigation.
Macdonald may be new to Line of Duty, but she is a well established actress in TV and film - from Trainspotting and Boardwalk Empire to Harry Potter, Brave and No Country For Old Men.
Line of Duty creator Jed Mercurio said: “We’re honoured that Kelly Macdonald will join Martin, Vicky and Adrian in series six of Line Of Duty. DCI Joanne Davidson will prove the most enigmatic adversary AC-12 have ever faced.”
Chatting to ITV’s Lorraine Kelly, he said: "Kelly plays DCI Joanne Davidson, who is the Senior Investigating Officer on a high-profile murder that remains unsolved over a year after the killing, and AC-12 get involved because there are question marks over her investigation."
What happened in season 5?
Line of Duty’s previous season saw undercover officer John Corbett (Stephen Graham) attempt to uncover the corrupt cop lurking within the Organised Crime Group – an individual known only as “H”.
His investigation leads him to believe the culprit is Ted Hastings, until the OCG manages to discover Corbett’s true identity and slit his throat.
‘H’ has still not been identified, while corrupt officer ‘Dot’ is dead and there appears to still be four rotten apple coppers infiltrating the force.
It is not known whether this season will be the last for Line of Duty, so fans could see some of their favourite characters outed as corrupt, or worse, killed.
When will season 6 be on TV?
Line of Duty series 6 returns on Sunday 21 March from 9pm on BBC One and BBC iPlayer.
It has also been confirmed that this season will have seven episodes, one more than usual.
There has been no date confirmed for when the latest season will debut, but it has been confirmed that it is expected soon.
Rumours in the beginning of 2020 had fans desperately waiting for the new season, but coronavirus led to difficulty filming and production was only finalised in November.
On 2 February, the BBC Press Office tweeted a video of Compston and Dubar in action, with the caption: “Listen up, fellas. When the gaffer asks for more, you better deliver.
“#LineOfDuty returns for Series 6 with an extra episode (7 instead of 6). Coming soon to
@BBCOne and @BBCiPlayer.”
In the teaser video, Steve (Compston) tells Superintendent Hastings (Dunbar): “Regardless of the personnel involved, Vella’s still the highest-profile inquiry engaging this force.”
Unconvinced, Hastings replies: “I’m gonna need a hell of a lot more before I can authorise a formal inquiry.”
Steve’s voiceover then adds: “How about an extra episode, gaffer?”
Where can I watch the first five seasons?
You can now watch all previous seasons of Line of Duty on the BBC iPlayer.