Detectives and police may have been employed by private railway companies in the United Kingdom almost right from the start of passenger services in the 1820s, with the first definitive reference dating to 1838.
A regulation of the Stockton and Darlington Railway refers to the police establishment of "One Superintendent, four officers and numerous gate-keepers".
Historical references (including those originating from the BTP itself) to when the first group of true "constables" was organised to patrol a railway should thus be treated with caution.
These personnel carried out their duties mostly in the open beside the track and were often dressed in a similar manner (e.g. a top hat and frock coat) to early police constables but were not directly concerned with law enforcement.
Occasional references to a "Police Department" in railway staff records at the National Archives relate to signalmen and others, although some of them were simultaneously county constables.