Watchmen were organised groups of men, usually authorised by a state, government, city, or society, to deter criminal activity and provide law enforcement as well as traditionally perform the services of public safety, fire watch, crime prevention, crime detection, and recovery of stolen goods. Watchmen have existed since earliest recorded times in various guises throughout the world and were generally succeeded by the emergence of formally organised professional policing.

In the late 1600s, the streets in London were dark and had a shortage of good-quality artificial light. It had been recognized for centuries that the coming of darkness to the unlit streets of a town brought a heightened threat of danger, and that the night provided cover to the disorderly and immoral, and to those bent on robbery or burglary or who in other ways threatened physical harm to people in the streets and in their houses.

In the 13th century, the anxieties created by darkness gave rise to rules about who could use the streets after dark and the formation of a night watch to enforce them. These rules had for long been underpinned in London and other towns by the curfew, the time (announced by the ringing of a bell) at which the gates closed and the streets were cleared. These rules, where codified by law, would come to be known as the nightwalker statutes; such statutes empowered and required night watchmen (and their assistants) to arrest those persons found about the town or city during hours of darkness. Only people with good reason to be out could then travel through the city. Anyone outside at night without reason or permission was considered suspect and potentially criminal.

Allowances were usually made for people who had some social status on their side. Lord Feilding clearly expected to pass through London's streets untroubled at 1am one night in 1641, and he quickly became piqued when his coach was stopped by the watch, shouting huffily that it was a 'disgrace' to stop someone of such high standing as he, and telling the constable in charge of the watch that he would box him on the ears if he did not let his coach carry on back to his house. 'It is impossible' to 'distinguish a lord from another man by the outside of a coach', the constable said later in his defence, 'especially at unreasonable times'.

The Ordinance of 1233 required the appointment of watchmen. The Assize of Arms of 1252, which required the appointment of constables to summon men to arms, quell breaches of the peace, and to deliver offenders to the sheriff, is cited as one of the earliest creations of an English police force, as was the Statute of Winchester of 1285. In 1252 a royal writ established a watch and ward with royal officers appointed as shire reeves:

By order of the King of England the Winchester Act Mandating The Watch. Part Four and the King commandth that from henceforth all Watches be made as it hath been used in past times that was to wit from the day of Ascension unto the day of St. Michael in every city by six men at every gate in every borough by twelve men in every town by six or four according to the number of inhabitants of the town. They shall keep the Watch all night from sun setting unto sun rising. And if any stranger do pass them by them he shall be arrested until morning and if no suspicion be found he shall go quit.

Later in 1279 King Edward I formed a special guard of 20 sergeants at arms who carried decorated battle maces as a badge of office. By 1415 a watch was appointed to the Parliament of England and in 1485 King Henry VII established a household watch that became known as the Beefeaters.

As of the 1660s, it was already common practice to avoid night-time service in the watch by paying for a substitute. Substitution had become so common by the late 17th century that the night watch was virtually by then a fully paid force.