‘Line Of Duty’ season 6 begins: Ranking the first five series of the hit BBC police drama

The author of this article has the right for his opinion to be questioned by a journalist at least one rank his senior.

It’s time to flush the SIM cards of your burner phones down the toilet… Line Of Duty is back.

After two long years, the police officers of Anti-Corruption Unit 12 (AC-12) return to our screens to do what they do best - nicking bent coppers. Or… failing to spot bent coppers working at the desk next to them.

What a relief it is to welcome back Superintendent Ted “like the battle” Hastings (Adrian Dunbar) and his two teacher’s pets, continuous cover-blowing Detective Inspector Kate Fleming (Vicky McClure) and waistcoated womaniser Detective Sergeant Steve Arnott (Martin Compston).

Read more: BBC reveals 'Line Of Duty' season 6 will have extra episode

Season 6 of the hit BBC series promises more dodgy police officers, more nerve-shredding interrogations and more bluster from the best Ted on TV since Super and Crilly. Mother of God!

But before it all begins on Sunday, 21 March, what is the definitive ranking of the five preceding seasons? Sit down, fella…

*WARNING: MAJOR LINE OF DUTY SEASONS 1-5 SPOILERS BELOW*

5. Line of Duty: Season Four

Bent copper: Detective Chief Inspector Roz Huntley (Thandie Newton).

Situation report (Sit rep): AC-12 take on the task of investigating Roz “13 going on 30” Huntley after forensic co-ordinator Tim Ifield (Jason Watkins) accuses her of framing the wrong man in the hunt for a serial killer.

Most shocking moment: The final shot of the first episode, when Huntley wakes up just as Ifield is about to carve her open with some hurriedly purchased power tools from his local DIY supplier.

Verdict: Unfortunately, Season 4 never manages to top that literally eye-opening shock. The five episodes that follow still make for a solid crime drama, but just aren’t on a par with the three previous riveting series.

Read more: Martin Compston teases 'massive bombshell' in season 6 of 'Line Of Duty'

Huntley is too underdeveloped to care about and even poor Steve being thrown down a flight of stairs feels tacked on. Oh, and couldn’t they have come up with a better suspect nickname than “Balaclava Man”?

4. Line of Duty: Season Five

Bent copper: Detective Sergeant John Corbett (Stephen Graham).

Sit rep: AC-12 are on the case when they suspect the involvement of an undercover copper after three police officers are killed in a drugs raid by an organised crime group (OCG).

Most shocking moment: Unquestionably the end of Episode 4, when Corbett’s dangerous game of trying to destroy the OCG from the inside finally results in his very sticky end.

Verdict: Operation Pear-shaped – I mean, Pear Tree – allowed Line Of Duty to shift focus from the cats to the mice, as viewers got their first long look inside one of the gangs linked to corrupt police officers.

But after the unhinged Corbett met his fate the diesel was sucked out of the rest of the series, despite a late interview room-stealing turn from Anna Maxwell Martin as Hastings-hater Detective Chief Superintendent Patricia Carmichael. Motherland of God!

3. Line of Duty: Season One

Bent copper: Detective Chief Inspector Tony Gates (Lennie James).

Sit rep: The first ever case for AC-12 sees them investigate supercop Tony Gates for fiddling his crime clearance rates, only to stumble into a world of murder, drugs and organised crime.

Most shocking moment: The end of Episode 2, when Jackie Laverty (Gina McKee) is murdered in her home in front of Gates. This scene announced that Line Of Duty was Game Of Thrones with cops — and that anything, and any character, was up for grabs.

Verdict: Rough around the edges and a far cry from the huge gun battle set-pieces in Season Five, Line Of Duty’s first outing may not have been as slick as later instalments, but then neither was DS Arnott’s facial hair.

Watch: 'Line Of Duty' season 6 teaser

Read more: It’s back! Line Of Duty return date announced

Driven by a remarkable performance from James — audiences could never quite tell if they were rooting for him or wanted him to get his comeuppance — the first season is urgent, blistering, must-see TV.

2. Line of Duty: Season Two

Bent copper: Detective Inspector Lindsay Denton (Keeley Hawes).

Sit rep: When a police escort of a protected witness is ambushed, the finger of blame — and AC-12’s gaze — is soon pointed at Lindsay Denton, the only officer to survive the attack.

Most shocking moment: Viewers are still angry at Line Of Duty writer/creator Jed Mercurio for having Detective Constable Georgia Trotman (Jessica Raine), barely in the show five minutes, thrown out of a hospital window at the end of the first episode.

Verdict: From its bamboozling opening (anyone who had a clue what was happening as Denton raced to assist the witness transport is either a liar or in on it) to its final episode flashback, Line Of Duty 2 took its predecessor’s strengths and bolstered them throughout.

The season’s trump card is Hawes’s portrayal of Denton, the TV cop audiences loved to hate… until her head was flushed down a toilet or her hands were covered in a kettle full of boiling water.

A wonderfully conflicted — and conflicting — character, Denton was the show’s dark heart.

1. Line of Duty: Season Three

Bent copper: Sergeant Danny Waldron (Daniel Mays).

Sit rep: When Waldron shoots a suspect dead and then instructs his team of authorised firearms officers (AFOs) to cover up the fact the deceased gave up his gun, AC-12 come calling.

Most shocking moment: Where do we start?! At the start, of course. Waldron packs more into a single episode than most TV characters manage in a five-season story arc.

First, he shoots dead a suspect, then covers it up, then holds his own against Hastings in one of the show’s most sofa-gripping police interviews, then tortures and murders a relative of the suspect he killed earlier, then gets shot himself.

Remarkably, the season gets even better after that, thanks largely to the performances of the returning Hawes as Denton and Craig Parkinson as Detective Matthew "Dot" Cottan, who is eventually outed as “The Caddy”, the police mole acting on behalf of organised crime.

Cottan’s murder of Denton, which he tries to pin on Arnott, is shocking enough, but it’s his dramatic and ultimately ill-fated urgent exit from the AC-12 interview suite that will go down in history as the show’s greatest WTF moment.

Verdict: Line Of Duty has always dealt in outrageous jaw-dropping revelations, but in its third series they have the most emotional heft. It helps that there is a focus on an actual series of crimes, in this case the historic sexual abuse of children, whereas the two series that followed perhaps pushed too hard with the chase to find the mysterious "H". Season three is peak LOD.

Watch: The best things to watch on Disney+ in March