Line of Duty season five has us hooked, but there's a question that's playing on everyone's mind — is it based on reality? The simple answer is no. The unit that Steve, Kate, and their colleagues are part of, AC-12, is completely fictional. However, there are anticorruption departments in the police force that fulfil a similar role, and there are police anticorruption officers that inspired the show.

Though the plots in Line of Duty may sometimes seem far-fetched, series creator Jed Mercurio has spoken about the importance of believability, saying: "I think it's important to be as close to the right procedures as possible. The starting point is with our advisers and I always get excited if we can use something I haven't seen in any other series."

The name AC-12 is close to the monikers of previous anticorruption branches in the real force. It used to be called A10 in the Met, before being changed to CIB1 and CIB2, and then the Directorate of Professional Standards. The units have changed their nicknames over the years, too. They were once know as the "Ghost Squad" or the "Untouchables." Their detectives were known as the "rubber heels" — because they had to operate in an unobtrusive way — or the less complimentary "muppets," which is what other detectives called them during their less effective days.