Line of Duty acronyms decoded–all the abbreviations explained, from OCG to GPR

Confused about the OCG's UCO or the MIT's SIO in Line of Duty? We've got your back

Vicky McClure as Kate Fleming in BBC's Line of Duty
(Image credit: BBC)

Even for the show's most seasoned fans, the many Line of Duty acronyms and abbreviations can be hard to keep up with.

From MIT to OCG and UCO, at times it feels like show creator Jed Mercurio gives us a new bit of Line of Duty lingo to learn every week. (For those who aren't up-to-speed with our favorite police drama, here's how to watch Line of Duty from outside of the UK.)

Episode one of the sixth series, for example, had pretty much everybody Googling, "what is a CHIS?" as a new abbreviation was introduced. Yep, they're pretty much as synonymous with the show as Ted Hastings sayings in Line of Duty

As we gear up for the Line of Duty Season 6 finale, here's a recap of the show's lingo from somebody who has rewatched the show more times than she cares to admit. 

What does OCG stand for in Line of Duty?

The OCG stands for Organised Crime Group, the corrupt gang that has ties to the police and which AC-12 has been on the scene since Line of Duty's very first season. 

Formerly led by Tommy Hunter, the group is assisted a corrupt network of police officers, and is the reason why we've all been asking ourselves, "who is H?" for the past few years. 

What is a CHIS in Line of Duty? 

This was a new one for the books at the start of Season 6—a CHIS is a covert human intelligence source, also known as an informant, who feeds information to the police relating to their investigations.

In the case of Line of Duty, the CHIS in Season 6 Episode 1 was Alistair Oldroyd, an informant for Central Police who passed on information relating to Gail Vella's murder. He was later found dead in apparent suicide—though the OCG could have staged this—and identified by his COM (that's Covert Operations Manager).

Martin Compston and Adrian Dunbar in BBC's Line of Duty

(Image credit: BBC)

What is a UCO in Line of Duty? 

A UCO is an undercover operative, an officer who is working undercover. The most famous in Line of Duty history is DS John Corbett, who managed to infiltrate the OCG as John Clayton before meeting his demise in Season 5.

DI Kate Fleming has also had a number of undercover operations in Seasons 1, 2 and 4, using the code names Kate Francis and Kate Flynn in the latter two. 

What is the GPR in Line of Duty? 

In the penultimate episode of Line of Duty Series 6, DI Kate Fleming ordered the GPR to look into what was under the concrete floor of the OCG's workshop. This stands for Ground Penetrating Radar and uses radio waves to investigate underground, without having to physically dig things up or disturb evidence. 

What is an SIO in Line of Duty? 

SIO stands for Senior Investigating Officer, the police officer heading up a particular investigation. 

Most recently, the team has looked into retired DCI Marcus Thurwell, who was the SIO on the Lawrence Christopher case. This is what journalist Gail Vella was looking into before she was murdered. 

We've rounded up a list of more Line of Duty acronyms for you to bookmark and refer back to next time you rewatch the show. 

More Line of Duty acronyms explained

  • SIO - Senior Investigating Officer
  • GPR - Ground-Penetrating Radar
  • CHIS - Covert Human Intelligence Officer
  • MIT - Murder Investigation Team 
  • DIR - Digital Interview Recording
  • OCG - Organised Crime Group
  • AFO - Authorised Firearms Officer
  • ARV - Armed Response Vehicle 
  • FI - Forensic Investigator 
  • UCO - Undercover Operative
  • COM - Covert Operations Manager
  • GSW - Gunshot wound
  • SFC - Specialist Firearms Command 

How to watch Line of Duty in the US and anywhere in the world

If you're outside of the UK and don't have a Hulu, Prime Video or Britbox subscription, you'll need a VPN to watch Line of Duty.

This is a really handy bit of software that changes your IP address so that streaming services like Netflix think you're in the UK.

Our sister site, TechRadar, has tested all of the major VPN services and they rate ExpressVPN as the absolute best. They say, "It's compatible with all of your devices, supports most streaming services, and ranks amongst the fastest. You can even install it on devices like an Amazon Fire TV Stick, Apple TV, Xbox, and PlayStation. So for a one-stop-shop, you can't go wrong with Express."

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(Image credit: Future)

We think we speak on behalf of the nation when we say that we can't wait to see how this season of the hit police drama wraps up.

Line of Duty Series 6 concludes on Sunday May 2nd at 9pm on BBC One 

Lucy Abbersteen

Lucy is a UK-based beauty journalist who has written for titles including Marie Claire, Glamour and OK!, as well as contributing to woman&home. Her work covers everything from expert skin and haircare advice to beauty trends and reviews of the latest products. During her career she regularly speaks to the industry's leading hairdressers, dermatologists and make-up artists, has covered backstage at London Fashion Week and interviewed many a celeb about their beauty routine.