Filming of the first series took place in Birmingham, England, before moving to Belfast, Northern Ireland, for the remainder of the programme.

The programme has been the subject of several accolades, including multiple nominations for British Academy Television Awards (BAFTA TV).

Line of Duty follows DS Steve Arnott, an authorised firearms officer who is transferred to Anti-Corruption Unit 12 (AC-12) after refusing to agree to cover up an unlawful shooting by his own team.

At AC-12 Arnott is partnered with DC Kate Fleming, a highly commended undercover officer with a keen investigative instinct.

They work under the supervision of Superintendent Ted Hastings, uncovering corruption within the fictional Central Police.

AC-12 realises the pervasive nature of corruption and the police's deep-rooted links to an organised crime group.

[7] Mercurio became an executive producer from the second series onwards, alongside Simon Heath for World Productions and Stephen Wright for BBC Northern Ireland.

[17] The special was promoted as a "deleted scene" from the fifth series and starred Compston, McClure, and Dunbar, along with Jason Isaacs and Lee Mack.

[18] A long-running story arc is the unknown identity of "H", a suspected corrupt police officer believed to be the highest connection to the organised crime group.

[28] Additionally, the story surrounding the Sands View Boys' Home in the third series included references to the Jimmy Savile sexual abuse scandal.

[32] Mercurio opted not to incorporate COVID-19 into the programme as four episodes of the sixth series had already been filmed when lockdown, face mask, and social distancing guidelines, were introduced and it would have been too expensive to re-film.

[22] Leading the main cast across the six series are Martin Compston and Vicky McClure, who portrayed Steve Arnott and Kate Fleming, respectively, two officers in AC-12.

[34] Each series features an additional actor as part of the main cast who portrays a police officer who is being investigated by AC-12.

[45] Mercurio also decided to bring Hawes back for the third series as a result of her character's positive reception and made changes to the script.

[47] Jessica Raine and Jason Watkins each appeared briefly in the second and fourth series, respectively, and were both credited within the main cast.

[52] She gave Hawes lower-end outfits to reflect "how far [Denton] had sunk in her grief", but also included power suits to show where "she would have been in her career if fate hadn't dealt her that hand".

She designed Davidson's apartment with "minimalist décor and cool tones" to illustrate it as a lonely place, while Buckells's office was expected to show his "shallowness and lack of commitment to his career".

[56] This room originally existed on location but had to be replicated on a sound stage during the COVID-19 pandemic and was built with no roof to allow for ventilation.

[66] Locations included BT Riverside Tower, McHugh's Bar, and Belfast City Hall.

[72] For the final series, Nettheim returned to direct alongside newcomers Gareth Bryn and Jennie Darnell.

[75] Once filming recommenced, changes to scripts were made to allow for social distancing because physical intimacy between performers had to be limited.

[22] Dunbar said in 2022 that he did not expect a full seventh series but anticipated the possibility of a three- to four- part miniseries or two 90-minute episodes.

[e][110] Following Kew Media Group's collapse in 2020,[111] Quiver Entertainment purchased international distribution rights for the first five series,[112] and ITV Studios acquired them for the sixth.

[113] Streaming rights for the sixth and any future series were exclusively issued to BritBox in the United States and Canada.

[114] In Canada and Australia, the series is available on Netflix and was briefly removed following uncertainty about the streaming rights after the Kew Media Group collapse.

[144] Metacritic, which uses a weighted average, assigned the series a score of 86 out of 100, based on 14 critics, indicating "universal acclaim".

Additionally, cast members McClure, Dunbar, Hawes, Newton, Macdonald, Mays, and Bonnar have all been nominated for acting-related accolades.

[157] Three scenes on the programme, "Urgent Exit Required", "Huntley's Narrow Escape", and "John Corbett's Death", received consideration for "Virgin TV's Must-See Moment".

[158][159][160] Composer Carly Paradis and director Andrew John McClelland have both been nominated for BAFTA Craft awards for their work on the show.

[161] Actors Graham and Compston have won Broadcasting Press Guild and TV Choice Awards.