The Chancellor and Vice-Chancellor of the University of Cambridge have the power to appoint and swear constables under the Universities Act 1825. Once appointed, such University constables have all the powers of a constable within a 5 mile radius of Great St Mary's church.
The principal function of the University Constabulary is to assist the Proctors. Normally there are between twenty and thirty University constables. The University Marshal and Vice-Marshal, who are senior constables, conduct the routine administration of the Constabulary through the Proctors' Office. Until the 1960s the Proctors and the Constabulary conducted regular street-patrols within the University precincts. Nowadays they operate on a reactive basis when disorder or demonstrations are expected.
In addition to its public-order function, the University Constabulary plays an important part in University ceremonial, at which it controls crowds, assists visitors and provides additional security at important events.