Who is Line of Duty's Kate Fleming?

DI Kate Fleming in Line of Duty
(Image credit: BBC/World Productions/Steffan Hill)

Everything you need to know about Kate Fleming!

Kate Fleming is everyone's favourite undercover copper from Line of Duty. She’s kept an eye on everyone’s behaviour throughout the show, and now looks set to be in hot water herself… could she be H?

Here’s everything you need to know about Kate Fleming as Line of Duty Season 6 arrives!

Who plays Kate Fleming?

Kate Fleming is played by actress Vicky McClure. Vicky has also appeared in Shane Meadows’ series This is England, the Amazon Prime Alex Rider series, Broadchurch and the BBC adaptation of The Secret Agent.

What rank is Kate Fleming?

As of Season 5, Kate is now a Detective Inspector.

Kate Fleming Line of Duty

Kate Fleming's look from Line of Duty Season 5.

Why is Kate so important?

Kate has been a major player in Line Duty from the get-go. She’s been DI Steve Arnott’s (Martin Compston) partner since the first season, where she was undercover at serious crime unit TO-20. There, she was investigating DCI Tony Gates for ‘laddering’, which is where you find someone guilty of one offence and then pile on additional charges afterwards.

In season 2, Kate went undercover once more. This time, she was stationed at Central Police’s Missing Persons Unit. She was investigating Lindsay Denton (Keeley Hawes). Kate did succeed in growing closer to Lindsay to start with, but eventually, her cover as Kate Foster was blown. 

Once Lindsay had figured Kate out, she lured Kate to a service station involved in the disappearance of Carly Kirk, where Lindsay confronted her. Since Kate had also been having an affair with Jane Akers’ husband, she had to be removed from the investigation.

Huge spoilers for Line of Duty ahead — If you’ve not caught up yet, don’t read on!

Season 3 was Kate’s biggest yet. She was placed undercover in Danny Waldron’s Strategic Firearms Command squad after Waldron shot Ronan Murphy. 

Kate was there to get more info from Waldron’s fellow officers about that operation. She was also present when Danny was killed by another member of his squad. At the scene of the crime, she tried to save his life whilst squadmates watched him bleed out.

Thanks to accusations of misconduct from Lindsay Denton, Kate’s working relationship with DS Arnott was put under strain. This led to her working more closely with DI Dot Cottan (Craig Parkinson).

Unbeknownst to AC-12, Kate had also been leading an undercover operation against her fellow AC-12 officers under the authority of AC-3. Despite the distance between Arnott and herself, Kate knew something was wrong with Dot’s approach to the investigation of The Caddy. 

This suspicion led to season 3’s explosive finale. This saw Kate chasing Dot, AKA "The Caddy", as he made his escape from AC-12. In a tense confrontation, Dot dived in front of Kate and saved her from being shot. In return, Kate recorded Dot’s dying declaration, giving a key piece of evidence in the fight against organised crime and police corruption. This launched the legendary question every Line of Duty fan desperately wants the answer to: Who is H?

Line of Duty


What happened in the latest seasons?

In season 4, Kate was once more undercover. This time, she was working on Operation Trapdoor at Central Police's Major Violent Crime unit. Unfortunately, she wasn't able to gather as much evidence as AC-12 wanted. Kate was constantly shut out of DCI Roz Huntley’s investigation into “Balaclava Man”. Someone else from inside AC-12 had leaked her operation to Huntley, which allowed her to build up strong defences to AC-12’s investigation across the season. 

Finally, season 5 saw Kate receive her promotion to DI. Here, her main role was as the voice of reason in AC-12’s investigation into the OGC and John Corbett (Stephen Graham). Steve was busy colluding with John Corbett for inside info on the OGC, and Ted Hastings (Adrian Dunbar) was growing more reckless in his investigation. Since Ted was now accused of being H, Kate stepped in as Commanding Officer, and succeeded in rescuing AC-12's reputation by identifying Gill Biggeloe as an OGC member.

What about Season 6?

In season 6, we were all shocked to learn that Kate Fleming no longer works for AC-12. During the first episode, she revealed that she left due to the changing dynamic at AC-12 following Ted's questionable behaviour. Now, she works for the Murder Investigations Team (MIT) with DCI Jo Davidson (Kelly McDonald).

Despite the great working relationship the two now share, Kate's loyalties have already been questioned. Thanks to a tip-off from another officer from the department, AC-12 has launched an investigation into MIT. Steve shows up unannounced to ask whether she would be willing turn traitor and work with him as an inside source.

Has Kate really left AC-12? Will she return? Only time will tell...

Line of Duty season 6 starts Sunday 21 March at 9pm on BBC1. For even more TV shows to enjoy, check out our TV guide. You can catch up on seasons 1-5 on BBC iPlayer right now!

Martin Shore
Staff Writer at WhatToWatch.com

Martin was a Staff Writer with WhatToWatch.com, where he produced a variety of articles focused on the latest and greatest films and TV shows. Now he works for our sister site Tom's Guide in the same role.

Some of his favorite shows are What We Do In The Shadows, Bridgerton, Gangs of London, The Witcher, Doctor Who, and Ghosts. When he’s not watching TV or at the movies, Martin’s probably still in front of a screen playing the latest video games, reading, or watching the NFL.