Criminal Investigation Department

The Criminal Investigation Department, (PROSE: Dominion) or CID, was a branch of police whose detectives wore "plain clothes". (TV: The Hungry Earth) Though not strictly speaking uniformed, they were typically well-dressed, (PROSE: The Hollow Men) frequently wearing ties. (PROSE: Cat's Cradle: Warhead)

Brighton had such a department, whose staff included Detective Inspector Bob Lines. (PROSE: Missing, Part One: Business as Usual) Trey Courte pretended to be CID, but was actually just a psychic who helped out the police with false credentials. (PROSE: Instruments of Darkness)

When Rory Williams walked out of the TARDIS — disguised as a police box — in 2020 to Ambrose Northover, she figured he must have been CID because of his lack of uniform. (TV: The Hungry Earth)