When is Line of Duty series 6 on TV? Who is in the cast?

Jed Mercurio’s bent copper series with Ted Hastings, Kate Fleming and Steve Arnott is coming back to screens – with a new guest lead

Line of Duty S5 - episode 3

Great news, fellas: series five of Line of Duty WON’T be the show’s last.

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The BBC1 drama following the intricate investigations of police anti-corruption unit AC-12 is set to return for at least one more run, with the BBC commissioning a sixth series before the fifth had even aired.

But when exactly will Jed Mercurio’s acclaimed thriller return to screens? Here’s everything you need to know about future episodes.


When will Line of Duty be back on TV?

Although series six has been given the green light, the BBC is yet to indicate when it might air.

Excluding the 12-month gap between series three and four, the BBC show has traditionally aired on a two-year cycle, so we might expect to along wait until spring 2021.

HOWEVER, Jed Mercurio told RadioTimes.com in October 2019 that Line of Duty might be back a lot sooner: “I would hope it’s sometime in 2020, next year.” And in November 2019 the BBC confirmed that filming would begin “next year”.


Who is the guest star for Line of Duty series 6?

The guest lead for series six of Line of Duty will be Kelly Macdonald, who will play DCI Joanne Davidson, “the senior investigating officer of an unsolved murder, whose unconventional conduct raises suspicions at AC-12.”

Kelly Macdonald

Line of Duty writer and showrunner, Jed Mercurio, says: “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.”

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


Who’s in the Line of Duty cast?

We can expect all the main AC-12 actors: Adrian Dunbar (Supt Ted Hastings), Vicky McClure (DI Kate Fleming), and Martin Compston (DS Steve Arnott) are all set to return.

It’s also possible Taj Atwal (PC Tatleen Sohota) and Aiysha Hart (Murder Squad cop DS Sam Railston) will make a comeback.

Polly Walker’s character Gill Biggeloe is still alive but has been given a new identity.  But this doesn’t completely rule out that her character will return – although going into witness protection at the end of series one, Tommy Hunter (played by Brian McCardie) returned in series two, albeit as a corpse.

Line of Duty S5 - Episode 5
Aiysha Hart as DS Sam Railston

As in previous years, we’re expecting some big guest stars to join the regular cast. We’ll find out more about these closer to the airdate.

And Jed Mercurio is already teasing us with some highly unlikely series six guest stars…

How to watch Line of Duty online

Ted Hastings Line of Duty (BBC)

What happened in Line of Duty series five?

You can see a summary of each episode here or read a (spoiler heavy) synopsis below…

  1. Line of Duty series 5: episode 1
  2. Line of Duty series 5: episode 2
  3. Line of Duty series 5: episode 3
  4. Line of Duty series 5: episode 4
  5. Line of Duty series 5: episode 5
  6. Line of Duty series 5: episode 6

The fifth run of Line of Duty centred on John Corbett (Stephen Graham), a rogue undercover officer who would go to any lengths to catch ‘H’, the corrupt copper at the heart of the Organised Crime Group (OCG).

As the series progressed, we learned that Corbett had links to AC-12 chief Ted Hastings. It transpired that Corbett’s mother, Anne-Marie, was a police informant who had a relationship – professional and perhaps more – with Hastings during The Troubles in Northern Ireland.

Thanks to lawyer Gill Biggeloe – who was secretly in league with the OCG – Corbett believed Hastings was responsible for Anne-Marie’s death at the hands of paramilitary forces. And, again due to Biggeloe, Corbett was determined to prove Hastings was a bent copper.

But his mission was cut short when the OCG discovered Corbett was a rat and slit his throat.

How did the OCG find out Corbett’s true identity? By the end of the series, it still wasn’t clear. According to OCG member Lisa McQueen, Corbett’s cover was blown thanks to a tip-off from Lee Banks, an imprisoned henchman from the same gang.

And where did Banks get this information from? Although never proven, many suspected Ted Hastings was the source. As AC-3 leader DCS Carmichael (Anna Maxwell Martin) theorised, Hastings could have leaked this intel as revenge – earlier in the series Corbett had beaten Ted’s wife.

After a large amount of bribe money was discovered in Hastings’ shabby hotel room, Carmichael then arrested him for conspiring to murder Corbett. And, going further, she intended to prove Hastings was ‘H’. However, this investigation only revealed that Biggeloe was actually trying to frame Ted for everything.

But although Hastings returned to active duty at the end of the series, he’s sadly not completely off the hook just yet…


Will series six be Line of Duty’s last?

In short: we’re not sure.

In a lot longer: Although the BBC hasn’t commissioned a seventh series, Mercurio certainly appears open to the idea. Rather than outright saying the sixth run would be the show’s last, he told the audience at the BFI & Radio Times Festival that he will be discussing future episodes with the BBC after series five has broadcast.

“Once series five has finished airing we’ll have a conversation with the BBC, with a view to whether there’s a possibility to series seven being commissioned. But we definitely know we’ve got series six,” he said.

Judging from series five viewing figures, a recommission seems likely. Its opening episode drew in a peak audience of over 8 million viewers, with an average of 7.8 million watching the entire episode — that’s larger than the season four finale in 2017.


Who is H?

Not one person, but four. Turns out that AC-12 had misinterpreted the dying testimony of Dot ‘The Caddy’ Cottan: instead of one police Kingpin called ‘H’, there’s actually a quartet of high-ranking police staff working with the OCG.

Looking back at the testimony, Steve Arnott and Kate Fleming noticed that Craig Parkinson’s character was tapping out the Morse code for ‘H’ on his left hand. Combining this signal with Cottan blinking at the letter ‘H’, the AC-12 detectives deduced he wasn’t trying to reveal the identity of one bent copper, but make it clear there’s four in the service.

Dot's dying declaration

In other words, there are four corrupt officers – and they’re NOT necessarily called ‘H’.

How much does this revelation change Line of Duty? At this stage in the show, not a lot. After all, as Fleming outlines, AC-12 has already discovered three of the four ‘H’s (again, just to clarify, their name doesn’t have to start with ‘H’). And they are…

  • DI Matthew Dot Cottan – as known as ‘The Caddy’
  • Lawyer Gill Biggeloe
  • Chief Superintendent Derek Hilton

There’s still one out there, though. As before, AC-12 are on the hunt for one corrupt senior member of the service.

The bad news? It could be anyone – their name doesn’t have to start with ‘H’. The good news? The final ‘H’ maybe isn’t as powerful as was feared – they were just one of four, not a single criminal mastermind.

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Where is Line of Duty filmed?

Previous series of the show have been filmed in Belfast, where the cast relocate during shooting.