Les Johnston 
Rebirth of Private Policing [PDF ebook] 

these are just two of the issues addressed by Les Johnston, who argues that policing, far from being the exclusive preserve of public personnel, is an activity undertaken by a mixture of public, private, and quasi-public agents. His book reviews the history of private policing, examines developments of current concern, and finally considers the implications of these developments both for the sociology of policing and for a more general understanding of public-private relations in the late 20th century.