Meet the cast of Line of Duty series 3

Daniel Mays – Sergeant Danny Waldron

Following Lennie James and Keeley Hawes into the spotlight this time around was Daniel Mays as Danny Waldron, an ambitious sergeant in a police armed response unit whose file crosses AC-12’s desk after the fatal shooting of a criminal suspect. It turned out that Waldron was on a mission of his own but one that was cut short by his mysterious death, surrounded by armed members of his own squad.

Mays is one of Britain’s most in-demand actors. Most recently seen as Private Walker in the big-screen remake of Dad’s Army, he played train robber Ronnie Biggs opposite Sheridan Smith in Mrs Biggs, and diarist Samuel Pepys in ITV’s The Great Fire.

Prior to that, he was revealed to be the Devil himself – and the cause of all Gene Hunt’s woes – in Ashes to Ashes, played a dad who’d unwittingly adopted an alien in Doctor Who, and starred with Anna Friel in the 2012 drama Public Enemies.

Feature films include Made in Dagenham, Welcome to the Punch and Atonement, while one of his earliest roles was as a pilot in Michael Bay’s Pearl Harbor.

Martin Compston – DS Steve Arnott

“Steve’s got a moral centre and he’s good at his job – but he’s arrogant and annoying.” That’s Martin Compston’s verdict on AC-12’s dogged investigator, who’s back for a third case.

Inverclyde-born Compston – who worked hard to master an English accent for Line of Duty – was previously a professional footballer, having helped Greenock Morton to relegation from the Scottish First Division in the 2001-2002 season. He got his acting break in Ken Loach’s acclaimed Sweet Sixteen, before taking a regular role as Ewan Brodie in the BBC’s Monarch of the Glen.

He appeared alongside Robert Downey Jr in A Guide to Recognizing Your Saints, and was nominated for a Scottish Bafta for his role in Andrea Arnold’s Red Road.

Vicky McClure – DC Kate Fleming

Series 2 saw undercover cop Kate Fleming’s personal life unravel so badly, she ended up sleeping in her car. When we meet her this time, she’s got a roof over her head and is working with a new team, so things are clearly looking up.

Vicky McClure came to prominence through her work with Shane Meadows, who cast her in his first film, A Room for Romeo Brass, after approaching her in a pub in their native Nottingham. Her role as former skinhead Lorraine “Lollipop Lol” Jenkins in Meadows’ This Is England series earned her a clutch of awards, including a Bafta for Best Actress.

Off-Duty, she’s probably best known for playing nosey tabloid journo Karen White in Broadchurch. Later this year, she’ll be reunited with This Is England co-star Stephen Graham for a BBC adaptation of Joseph Conrad’s Victorian spy thriller The Secret Agent.

Adrian Dunbar – Supt Ted Hastings

AC-12 boss Hastings spent much of series 2 trying to stop his own life becoming a focus for police investigation – and things aren’t looking any easier for him this time round.

Adrian Dunbar found fame as the lead and co-writer of the 1991 film Hear My Song. The following year, the Enniskillen-born actor appeared in Neil Jordan’s The Crying Game, and in 1993 was the focus of Robbie Coltraine’s first case as the prime suspect in the opening episode of Cracker.

Since then, he’s barely been off our screens, juggling a hugely acclaimed stage career with appearances in everything from A Touch of Frost to Death in Paradise.

One place he wasn’t on screen, though, was in Star Wars: The Phantom Menace: his role as Princess Leia’s adoptive father, Bail Organa, was cut from the film, and re-cast with Jimmy Smits for Episode II. Consider it a lucky escape.

Craig Parkinson – DS Matthew Cottan

Matthew “Dot” Cottan is the rotten apple at the heart of AC-12. Will series 3 finally see him get his comeuppance? We’ve got everything crossed.

Craig Parkinson’s first TV role was in a 2001 episode of Dalziel and Pascoe, and he made his big screen debut as Factory Records guru Tony Wilson in Anton Corbijn’s Ian Curtis biopic, Control. He played lecherous probation worker Shaun in E4’s Misfits, and beat Tom Hardy to the punch – literally – playing boxing twins Jimmy and Johnny Kray in ITV’s Whitechapel.

The 6’ 4.5” actor is married to Susan Lynch – most recently seen wielding that shotgun in Happy Valley.

Keeley Hawes – Lindsay Denton

Where to start? DI Lindsay Denton was sentenced to life in prison for conspiracy to murder at the end of two, a conviction she succeeded in quashing in a shock return for series three. Now she's attempting to rebuild her life – but with a criminal conviction for conspiracy to pervert the course of justice, will her dream of rejoining the police force ever be realised?

Keeley Hawes first made her name playing a young Diana Dors in The Blonde Bombshell before Tipping the Velvet, Ashes to Ashes and Spooks put her name firmly on the map. The actress met her husband, Matthew Macfadyen on the latter and went on to star in the BBC's short-lived adaptation of Upstairs Downstairs between 2010 and 2012.

But it was Line of Duty that delivered a role which allowed Hawes to showcase her full dramatic range. The question of DI Denton's guilt captivated TV audiences during the drama's second series and earned Hawes a Bafta nomination. Since then, she's gone on to appear in The Casual Vacancy, Doctor Who and The Durrells (currently airing on ITV) and will next be seen in The Hollow Crown alongside Benedict Cumberbatch and Judi Dench.

Polly Walker – Gill Bigelow

Warrington-born Walker landed a plum first acting job when she was cast in the title role of ITV's 1990 adaptation of Lorna Doone, co-starring Clive Owen and Sean Bean.

She appeared in the films Enchanted April and Patriot Games, with Harrison Ford, and played John Simm's wife Anne in Paul Abbott’s State of Play. She’s also had regular TV roles in Rome (which earned her a Golden Globe nomination), Battlestar Galactica spin-off Caprica, The Syndicate and Mr Selfridge (pictured), where she played Delphine Day.

Jonas Armstrong – Joe Nash

Jonas, like Danny, was a young resident of Sandsview children's home and a victim of sexual abuse at the hands of Ronald and Linus Murphy and – in particular – Dale Roach. Haunted by his experience, Jonas is working with DC Arnott to bring the perpetrators to justice.

Jonas Armstrong first appeared in Teachers and The Ghost Squad but is best known to many as Robin Hood, appearing in the BBC drama for three series before departing in 2009.

He has since gone on to act in The Body Farm, Prisoners' Wives and Ripper Street and will next be seen in ITV's Joanne Froggatt drama Dark Angel.

Will Mellor – PC Rod Kennedy

Rod Kennedy was a member of Danny Waldron's emergency response squad and present during Waldron's death. Caught up in the investigation – and conflicted by his relationship with colleague Jackie Brickford – Rod was found hanged in an apparent suicide, although it was subsequently proven that he had been murdered.

The former Hollyoaks heartthrob (he once had a number 5 hit with a cover of Leo Sayer’s When I Need You, you know) plays a member of Danny Waldron’s armed response unit in the new Line of Duty.

Mellor has been a regular TV face for more than 25 years since making his debut on Children’s Ward, with roles ranging from Jack Vincent in Casualty to 10 years as Gaz Wilkinson in Two Pints of Lager and a Packet of Crisps.

More recently, he played Steve Connolly in Broadchurch, and starred in two series apiece of comedies White Van Man and In with the Flynns. Other career highlights include voicing a dog in the CITV series Barking!, winning the first series of Comic Relief Does Fame Academy, and modelling for Topman.

Arsher Ali – Ali PC Harinderpal ‘Hari’ Bains

Royal Shakespeare Company regular Ali – who plays another member of Waldron’s firearms team – came to prominence as a would-be suicide bomber in Chris Morris’ Four Lions.

Since then, he’s had major roles in the likes of Beaver Falls, Complicit and The Missing, co-starred alongside Martin Clunes in ITV’s adaptation of Julian Barnes’ Arthur & George, and appeared in last year’s watery Doctor Who two-parter Under the Lake / Before the Flood.

Leanne Best – WPC Jackie Brickford

A veteran of such Brit TV staples as Casualty, New Tricks and Doctors, Leanne Best – here playing a firearms officer – is probably best known as Jane Cobden in Ripper Street, Celia Donnelly in Fortitude and teacher Teresa Fenchurch in ITV’s Home Fires.

She also has a blink-and-you’ll-miss-it role as Min Sakul in Star Wars: The Force Awakens.

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George Costigan – Retired Chief Supt Patrick Fairbank

Retired from the force, Fairbank becomes a person of interest for DC Arnott and DS Fleming. But will his personal connections protect him from their investigations?

On television screens since 1978, George Costigan first found fame as adulterous businessman Bob in Rita, Sue and Bob Too. He's since gone on to appear in The Adventure of Sherlock Holmes, Kavanagh QC, Inspector Morse and New Tricks, plus a guest role in the 2007 Doctor Who Christmas special.

In the theatre, he originated the role of Mickey Johnston in Blood Brothers. He also spent six months appearing on Emmerdale in 2009 and most recently played Nevison Gallagher in both series of Happy Valley.

Shaun Parkes – Chief Supt Terry Reynolds

Following roles in the likes of Soldier, Soldier, Casualty and Heartbeat, Shaun Parkes got his big break in the movie Human Traffic (pictured). Other film work includes The Mummy Returns, Things to Do Before You’re 30 and Notes on a Scandal.

He played Rocco in Russell T Davies’ Casanova, and reunited with David Tennant for The Impossible Planet / The Satan Pit – the 2006 Doctor Who two-parter that gave the world the Ood. In 2009, he played the title role in BBC2's acclaimed detective thriller Moses Jones, assisted by another Time Lord, Matt Smith.

Aiysha Hart – DS Sam Railstone

Another new cast addition, Hart is best known for playing Ariadne in the BBC’s short-lived sword and sandals fantasy Atlantis (pictured).

The daughter of English and Saudi Arabian parents, Hart – who says she’s “semi-fluent” in Arabic – also took the lead in the 2014 thriller Honour, co-starring Paddy Considine.