(law enforcement) A police officer tasked with collecting evidence and information in order to solve a crime; an investigator.
He worked as a detective with the agency for five years.
A person employed to find information not otherwise available to the public.
Had they responded this way in France or America, this wouldn't have surprised me, but wasn't everyone in England supposed to be a detective? Wasn't every crime, no matter how complex, solved in a timely fashion by either a professional or a hobbyist? That's the impression you get from British books and TV shows. Sherlock Holmes, Miss Marple, Hetty Wainthropp, Inspector George Gently: they come from every class and corner of the country. There’s even Edith Pargeter's Brother Cadfael, a Benedictine monk who solved crimes in twelfth-century Shrewsbury. No surveillance cameras, no fingerprints, not even a telephone, and still he cracked every case that came his way.