" superintendents, chief inspectors, inspectors, sergeants and constables. If an officer works for CID (Criminal Investigation Department), then he or she will carry the prefix D (for Detective). A DCI is a detective chief inspector, DI is a detective inspector, DS a detective sergeant, and DC a detective constable. Officers not assigned to CID would wear a uniform. (Rebus sometimes refers to these unfortunates as “woolly suits.”) Lowest in the pecking order are the PC (police constable) and WPC (woman police constable). "

― Ian Rankin , Resurrection Men (Inspector Rebus, #13)