What does CID mean in British policing?

The Role of the Criminal Investigation Department (CID)

When people picture police detectives, they are usually thinking of the Criminal Investigation Department (CID). Operating across the United Kingdom and numerous Commonwealth nations, the CID is the specialized branch housing the vast majority of plainclothes investigators.

While regular uniformed police officers handle day-to-day patrols and immediate public safety calls, CID detectives dive deep into solving serious offenses, questioning witnesses, and building solid cases. It is worth keeping in mind that a police force's CID is entirely separate from its Special Branch, though members belonging to either unit proudly carry the "Detective" rank prefix.