The establishment of the Metropolitan Police by Sir Robert Peel in 1829 had proved successful, so in 1842 the first Detective Branch was created with the purpose of preventing crime rather than undertaking post factum investigations. Two detectives were attached to each division of the force and two inspectors and six sergeants were established at Scotland Yard. In the event, the detectives' success in tracking down murders, and especially in the Manning case in 1850, changed public perceptions and their mode became forensic.
Detectives soon began to appear in fiction, Dickens' Inspector Bucket in Bleak House (1852) and Wilkie Collins's Serjeant Cuff in The Moonstone (1868) being two famous examples. …
Editors. "Detective Branch of the Metropolitan Police formed". The Literary Encyclopedia. First published 12 December 2007
[http://www.litencyc.com/php/stopics.php?rec=true&UID=5480, accessed 25 April 2017.]