Line of Duty: The Complete Guide to the BBC's Anti-Corruption Drama

Few British crime dramas have built the same level of obsessive, clue-hunting fandom as Line of Duty. Created by Jed Mercurio, the series turns the police procedural inside out: instead of chasing criminals on the street, the officers of AC-12 chase corruption inside their own ranks. The result is a tense, interview-room-driven thriller that has set UK viewership records and turned phrases like "bent coppers" and "Mother of God" into cultural shorthand.

This guide breaks down the series in order, introduces the core cast and recurring storylines, explains the long-running "H" mystery, and points you to where you can watch it. Whether you are starting fresh or preparing for the upcoming seventh series, here is everything you need to know.

What Is Line of Duty About?

Line of Duty: Series Guide, Cast, Watch Order & Why It Works - What Is Line of Duty About?.

Line of Duty follows Detective Sergeant Steve Arnott, a former counter-terrorism officer who is transferred to Anti-Corruption Unit 12 after refusing to cover up an unlawful shooting by his own team. At AC-12, he works alongside Detective Constable Kate Fleming and Superintendent Ted Hastings to investigate corrupt officers within the fictional Central Police force.

Each series introduces a new central suspect: a police officer who appears respectable on the surface but may be entangled in serious criminal activity. The AC-12 team builds a case through interviews, surveillance, financial records, and careful procedural work. What starts as a single investigation gradually reveals a wider network of organized crime with links to senior police ranks.

The show is known for its extended interrogation scenes, where a suspect's carefully constructed story is dismantled line by line. These scenes are the dramatic core of the series: quiet, methodical, and often devastating.

Line of Duty Series Guide and Watch Order

Line of Duty: Series Guide, Cast, Watch Order & Why It Works - Line of Duty Series Guide and Watch Order.

The series should be watched in broadcast order. Each season builds on the previous one, and the overarching "H" storyline becomes more important from series three onward.

Series 1 (2012)

The opening series introduces Steve Arnott and his transfer to AC-12. The team investigates DCI Tony Gates, a highly decorated officer whose perfect record hides a dangerous pattern of manipulation. Lennie James plays Gates, and the series establishes the show's signature structure: a charismatic suspect, a mounting case, and a tense final interview.

Series 2 (2014)

Keeley Hawes stars as DI Lindsay Denton, a complex suspect connected to an ambush that leaves protected witnesses dead. Series two sharpens the show's moral ambiguity and delivers one of its most memorable interrogation sequences. The season also deepens the personal stakes for the AC-12 team.

Series 3 (2016)

Sergeant Danny Waldron, played by Daniel Mays, is the focus of the opening investigation. His case connects to a historic abuse scandal at a boys' home and introduces the first explicit hints of a senior corrupt figure known as "H." The series ends with a major shift in the show's mythology.

Series 4 (2017)

Thandiwe Newton plays DCI Roseanne Huntley, a senior officer under investigation for mishandling evidence. Series four was the first to air on BBC One after the show's promotion from BBC Two, reflecting its growing audience. The season tightens the connection between individual corruption cases and the wider organized crime network.

Series 5 (2019)

Stephen Graham joins the cast as DS John Corbett, an undercover officer whose loyalties are dangerously unclear. The "H" investigation accelerates, and the series begins to narrow the list of possible suspects. Series five also explores Ted Hastings' own vulnerability to suspicion.

Series 6 (2021)

Kelly Macdonald stars as DCI Joanne Davidson, a guarded officer linked to the murder of journalist Gail Vella. The sixth series became a national viewing event in the UK, with millions tuning in for the finale. The reveal of "H" divided critics and fans, but the season cemented the show's place as one of the most-watched British dramas of the modern era.

Series 7 (Expected 2027)

The BBC confirmed in November 2025 that a seventh series has been commissioned, with Martin Compston, Vicky McClure, and Adrian Dunbar returning. Filming is scheduled to begin in Belfast in spring 2026, with broadcast expected in 2027. Plot details remain tightly guarded, but the announcement confirms the story is not finished.

Core Cast and Characters

Line of Duty: Series Guide, Cast, Watch Order & Why It Works - Core Cast and Characters.

DS Steve Arnott — Martin Compston

Arnott begins the series as a principled officer whose refusal to participate in a cover-up costs him his place on a firearms team. At AC-12, he becomes a skilled investigator, though his own judgment and personal life are repeatedly tested. Compston has played the role across all six series and will return for the seventh.

DC Kate Fleming — Vicky McClure

Fleming is an experienced undercover officer with sharp instincts. Across the series, she moves between AC-12 and deep-cover assignments, often placing herself in direct danger. Her partnership with Arnott forms the emotional backbone of the show.

Superintendent Ted Hastings — Adrian Dunbar

The head of AC-12, Hastings is a by-the-book leader with a strong moral code and a memorable line in exasperated expressions. Dunbar's performance has made Hastings one of the most quoted characters in modern British television. His own integrity becomes a central question in later series.

Notable Guest Leads

Each series introduces a high-profile guest lead, often playing the officer under investigation:

• Lennie James as DCI Tony Gates (series 1)
• Keeley Hawes as DI Lindsay Denton (series 2)
• Daniel Mays as Sergeant Danny Waldron (series 3)
• Thandiwe Newton as DCI Roseanne Huntley (series 4)
• Stephen Graham as DS John Corbett (series 5)
• Kelly Macdonald as DCI Joanne Davidson (series 6)

The "H" Mystery Explained

Line of Duty: Series Guide, Cast, Watch Order & Why It Works - The "H" Mystery Explained.

The show's longest-running storyline is the search for "H," a corrupt senior police officer believed to be the highest connection to the organized crime group operating inside Central Police. The name first appears at the end of series three, when a dying character spells out part of a name.

Jed Mercurio has said he deliberately gave multiple characters names beginning with "H" so that the story could evolve. This ambiguity fueled years of fan theories, with viewers analyzing freeze-frames, background details, and even the spelling of names. The series six finale provided an answer, though not one that satisfied every viewer.

For new viewers, the "H" arc is best experienced without spoilers. The mystery works because the show plants clues early and rewards close attention, but the emotional weight comes from what the investigation does to the AC-12 team itself.

Where to Watch Line of Duty

Availability varies by region. In the UK, the series originally aired on BBC Two and later BBC One, and episodes are typically available through BBC iPlayer. Internationally, the show has appeared on Netflix in some territories, though current availability depends on your country and licensing agreements.

Check your local streaming platforms for current availability. The show's international distribution has been complicated at times, which has contributed to its cult following in some regions and delayed availability in others.

Why Line of Duty Works: The Interview Room as Battlefield

The show's most distinctive feature is its use of the police interview as a dramatic set piece. While many crime dramas rely on chases and shootouts, Line of Duty builds tension through language: the careful wording of a question, the pause before an answer, the slow reveal of a document the suspect did not expect.

These scenes work because the writing treats procedure as drama. The audience learns the rules of police conduct alongside the characters, so every procedural misstep carries weight. When a suspect says "no comment," it is not a dead end but a strategic move in a longer game.

The series also benefits from moral complexity. Suspects are rarely purely evil. Many are competent officers who made one bad decision and then compounded it. This makes the investigations feel grounded and raises uncomfortable questions about institutional loyalty, whistleblowing, and the cost of doing the right thing.

How Line of Duty Reflects Real Policing Concerns

Several storylines draw on real events. The opening scene of series one echoes the 2005 shooting of Jean Charles de Menezes, a man wrongly identified as a suicide bomber. The Sands View Boys' Home storyline in series three references the Jimmy Savile abuse scandal. The murder of journalist Gail Vella in series six was inspired by the 2017 assassination of Maltese journalist Daphne Caruana Galizia.

These connections give the fiction a sharper edge. The show is not a documentary, but its willingness to engage with real institutional failures makes its fictional corruption feel plausible rather than cartoonish.

What to Watch After Line of Duty

If you have finished all six series and are waiting for series seven, several other shows explore similar territory. Bodyguard, also created by Jed Mercurio, shares the same tension-driven style and features Keeley Hawes in a leading role. Happy Valley offers a different but equally gripping take on British policing. For a more international perspective, The Wire remains the benchmark for dramas about institutional corruption.

For fans drawn to the show's procedural detail and long-form investigation structure, the appeal is similar to well-built systems: each piece matters, and the whole only makes sense when you see how the parts connect.

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Sources and further reading

• Line of Duty (TV Series 2012– ) - IMDb - Storyline. Edit. Line of Duty follows Detective Seargent Steven "Steve" Arnott (Martin Compston), a former authorized firearms officer who led an operation to ...
• Line of Duty - Line of Duty is a British police procedural and serial drama television programme created by Jed Mercurio and produced by World Productions for the British Broadcasting Corporation (BBC). It began broadcasting on BBC Two on 26 June 2012. The programme performed well and was quickly commissioned for additional series that aired in 2014 and 2016. After becoming the highest-rated series on BBC Two in 10 years, Line of Duty was promoted to BBC One, beginning with the fourth series in 2017, the fifth in 2019, and the sixth in 2021. A seventh series is currently in production and is scheduled to air in 2027.
• Watch Line of Duty | Netflix - Detective Sgt. Steve Arnott is transferred to a police anti-corruption unit after refusing to be part of a cover-up involving an accidental shooting.

Frequently Asked Questions

Do I need to watch Line of Duty in order?

Yes. Each series builds on the previous one, and the overarching "H" storyline becomes increasingly important from series three onward. Watching in broadcast order is the best way to understand character motivations and the wider conspiracy.

Is Line of Duty based on a true story?

The series is fictional, but several storylines draw on real events, including the shooting of Jean Charles de Menezes, the Jimmy Savile scandal, and the murder of journalist Daphne Caruana Galizia. The show uses these references to ground its fictional corruption cases in recognizable institutional failures.

Who is H in Line of Duty?

The identity of "H" is revealed in the series six finale. The reveal was divisive among fans, but the show's creator has defended the choice as consistent with the series' themes. For new viewers, it is best to avoid spoilers and let the mystery unfold.

Will there be a Line of Duty series 7?

Yes. The BBC confirmed in November 2025 that a seventh series has been commissioned. Martin Compston, Vicky McClure, and Adrian Dunbar will return, with filming expected to begin in Belfast in spring 2026 and broadcast scheduled for 2027.

Where can I watch Line of Duty?

Availability varies by region. In the UK, episodes are typically available on BBC iPlayer. Internationally, the show has appeared on Netflix in some territories, but current availability depends on your country. Check your local streaming services for the most up-to-date information.

How many episodes are in Line of Duty?

There are 36 episodes across six series, with a seventh series in production. Episode lengths range from roughly 57 to 88 minutes, with finales often running longer.

Conclusion

Line of Duty earned its reputation by treating police corruption as a structural problem rather than a series of isolated bad apples. Its interview-room confrontations, morally complicated characters, and slow-burning conspiracy created a drama that rewards patience and close attention. With a seventh series confirmed, the story of AC-12 is not over yet.

Whether you are starting from the beginning or revisiting the clues before the new series, the best approach is the same one the show demands of its characters: pay attention to the details, question everything, and do not assume anyone is above suspicion.

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