Line of Duty series 6: Trailer, release date, cast and plot - everything you need to know

The wait is finally over - Line of Duty is back on our screens.

The hit British police drama was re-commissioned for a fifth and sixth season at the end of season four back in 2017, yet with production delays in 2020 because of the coronavirus pandemic, it's only now that the sixth season has surfaced.

Here’s everything we know about Line of Duty season 6 on BBC One so far, including whether the anti-corruption squad will continue after that...

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Line of Duty season 6 finale trailer

If you weren't already excited enough, the BBC has released a white-knuckle trailer for the final episode of Line of Duty season 6.

It looks like we can expect more action, more interviews and finally get the big reveal on 'H' and the Fourth Man.

Will it be Osborne, Carmichael, Davidson, Ted, Kate or that scary looking prison guard? We'll have to tune in on Sunday night to find out.

Line of Duty episode reviews and theories

Episode 1: The CHIS, Farida and Buckells

Episode 2: Who killed Gail Vella?

Episode 3: Is there something fishy about Lomax?

Episode 4: Who is Jo Davidson's relative?

Episode 5: Who got shot?

Episode 6? Who is the Fourth Man?

How can I watch Line of Duty season 6?

The sixth series of Line of Duty launched on Sunday, March 21, at 9pm on BBC One and BBC iPlayer, with new episodes airing weekly.

A 'Memo to AC12 staff' released to press - and a clip featuring Ted Hastings (Adrian Dunbar) and Steve Arnott (Martin Compston) - also revealed that there are seven episodes in the new series. Mother of God!

When was series 6 filmed?

The show's creator and writer Jed Mercurio confirmed filming had ended at the end of November and a new picture from the show was released to mark the occasion.

The image featured Kelly Macdonald (Trainspotting, Boardwalk Empire), who joins the show as Detective Chief Inspector Joanne Davidson, the senior investigating officer on an unsolved murder case whose unconventional conduct attracts the attention of AC-12.

Filming for series 6 had begun in February 2020, in Belfast, Northern Ireland - but was suspended a month later when the first Covid lockdown hit. It wasn't until September 2020 that filming restarted.

Posting a picture of crew members and Martin Compston wearing face masks, Mercurio thanked the "dedicated cast and crew for keeping the #LineofDuty filming CoViD safe".

Simon Heath, Executive Producer for World Productions, confirmed that the show has implemented "all the industry Covid protocols", and filming is in accordance with current government guidelines on COVID-19.

Ahead of the new series, Mercurio stated: "We have taken lots of precautions for cast and crew. We have filmed on studio sets which is a departure from previous series where we have shot in an actual working building. The reason why is because we can ventilate the set and social distance our cast and crew. We have had rigorous measures in place during the shoot."

Who’s in the cast?

It's been confirmed that the three main three cast members are returning for series 6. That’s Vicky McClure (DI Kate Fleming), Martin Compston (DS Steve Arnott) and Adrian Dunbar (Superintendent Ted Hastings).

Anna Maxwell Martin has also been confirmed to return in episode 5 as Detective Chief Superintendent Patricia Carmichael - the no-nonsense independent investigator from AC-3 who was brought in after suspicions mounted over Hastings.

And as well as Kelly Macdonald joining the show, there's also a new member of AC-12 in series 6: Shalom Brune-Franklin joins the show as DC Chloe Bishop.

Whether they’ll all survive for the whole series remains to be seen, as the show’s creator and writer Jed Mercurio has a habit of killing off the show’s main characters.

Superindent Ted Hastings - Adrian Dunbar

Adrian revealed that Hastings has issues outside of work in this new series.

"Quite a lot has happened and there’s been quite a time jump," he revealed.

"In his working life, a lot of things have destabilised which have affected the unit. I think he’s another year older but not another year wiser. 

"Let’s face it – time is running out a bit for Ted; the age he is, whether he can stay in the force, is he useful enough, is he a bit of a dinosaur? He’s up against quite a bit. His personal life is not in great shape."

DS Steve Arnott - Martin Compston

Martin revealed DS Arnott is struggling both mentally and physically in the new series.

He explained: "At the beginning of the series, Steve is still a DS. So, still no promotion but he is chasing! He has got bored as AC-12 is now tainted and the investigations have been severely curtailed.

"At the start, he is chasing up mundane cases; similar to chasing Lennie James over the expense of a bacon roll in the first series! Steve thrives on the thrill of the chase and the adventure of it so he’s a bit lost and having issues both physically and mentally.

"He definitely sees himself as a bit of a Sherlock Holmes with a waistcoat."

DI Kate Fleming - Vicky McClure

Vicky was full of praise for newcomer Kelly Macdonald.

"Kelly is a great laugh and an incredible actor. Again, we were really grateful to have a new guest lead that fits straight into the Line of Duty family," she said.

"We had some brilliant scenes to do together and enjoyed many jigsaws together! I think everyone will be blown away with Jo’s storyline. It couldn’t have been in better hands."

DCI Joanne Davidson - Kelly Macdonald

Kelly said of her character: "At the start of the series, she’s quite a lonely figure. She’s struggling and we don’t quite know why that is.

"She’s doing very well in her career. She’s the head of an important case and it’s very high profile. 

"She’s got a very stressful position and deals with it well but is quite a closed off person. There’s a lot going on under the surface with her. She gets to the point where she has to make tricky decisions. "

Kelly is best known for her roles in Trainspotting, Gosford Park, State Of Play, No Country For Old Men, Boardwalk Empire and, most recently, The Victim and Giri/Haji. 

Line of Duty writer and showrunner Jed Mercurio, said at the time of her casting announcement: "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."

DC Chloe Bishop - Shalom Brune-Franklin

Shalom said she was thrilled to get the part of DC Chloe Bishop.

"I remember receiving an email that said ‘LOD6’ and I thought oh it’s an audition for a show called ‘Lod’. It didn’t click in my head that it was Line of Duty. I opened the email and I saw the words ‘Anti-Corruption Unit 12’ and I shrieked. I freaked out," she said.

"I was so nervous but there were so many lines to learn that in a way, it took away my nerves. It was mad.

"I was such a fan of the show and it was such a surreal experience to get to walk onto the set of something you are already such a huge fan of. I was over the moon to get the job! Line of Duty has so many people in it creatively that I look up to and admire. To be a part of that is quite unbelievable."

She said of her character: "Chloe is the newest member of AC-12. Like anyone starting a new job, she’s so eager to prove to her bosses that she was the right choice. She’s incredibly hardworking and we can see she’s really trying to impress."

DCS Patricia Carmichael - Anna Maxwell Martin

Anna Maxwell Martin said of her character's return: “Pat’s back, I can’t remember what she’s doing there, nor would I be allowed to blab, but suffice to say she’s got some new clobber and she’s ready to bust some balls."

Who is H in Line of Duty? 

Season 5 of Line of Duty was set up around answering one of telly’s most burning questions: Who is the corrupt police officer, known as H?

By the finale, we'd discovered that H was not one person, but was actually made up of four Caddies, signalled by original Caddy DI Matthew 'Dot' Cottan who the team noticed had been tapping out the Morse Code for H - four dots - in his dying declaration.

What will happen in series 6?

We know that ACC Derek Hilton was the second part of H, and series 5 named legal counsel Gill Biggeloe as the third, so we're expecting to see AC-12 searching for the fourth and final corrupt official in series 6.

Hastings is still a strong possibility despite being framed by Biggeloe in series 5, and AC-3's DCS Patricia Carmichael who was investigating him also looks decidedly dodgy.

Meanwhile, OCG member Ryan's success in getting into police college will surely be followed up as he becomes the force's newest corrupt officer.

Creator Jed Mercurio kept his cards close to his chest on the new series.

"This series, AC-12 will investigate what’s going on at Hillside Lane Police Station in a case led by DCI Joanne Davidson and we look at the investigation of a cold case," he revealed.

"It’s the high-profile murder case of Gail Vella that has remained unsolved for over a year and which the police force is struggling to solve. There’s been no closure."

Speaking to journalists including BT.com to promote the fifth series, Martin Compston hinted that storylines would be further developed - and potentially come to a conclusion - in series 6.

“The BBC have been really good to us," he said.

"Ever since series 2, we’ve been commissioned for two at a time... because Jed has been very adamant that he’s going to be the one that finishes it, so if he doesn’t know if we’ll get a series 7 or 8, then he will [finish it]. 

“His thing is he has to give the pay-off to the audience, who have stuck with us all these years. It gives him the breathing space to go ‘I can develop this over next series, because I know we’re going to be there’, so that’s been great.”

Will there be a series 7?

Line of Duty has only been commissioned up to season 6, with its creator Jed Mercurio telling journalists that the show has "a life span". Does this mean that the new series will be its last?

Asked how long Line of Duty can go on for, Mercurio said at a press screening ahead of the fifth season: “I don’t know. We all love making the show. I think a lot depends on how people respond to it.

“I think that it’s great that people get very excited about it, when they get to the end of the series and they talk about what they want to know, and what they want to see next.

“But I think we recognise that it’s got a life span, so I think we’ve got to calibrate that against the audience responses.

“I have some thoughts [about how it’s all going to end].”

Is there a trailer?

Yes! The BBC has released this official trailer:

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The Line of Duty season 6 finale is at 9pm on Sunday, May 2, on BBC One and BBC iPlayer.

Catch up on all five seasons of Line of Duty on BBC iPlayer, and with season 5 on Netflix.