The later 19th century saw the formation of two distinct visions of serious criminality. Previous studies of the weak-willed, ‘degenerate’ offender, have neglected the simultaneous appearance of the modern professional criminal. This essay reveals that the rise of the security industry in the Victorian era served to reshape notions of criminal professionalism, imbuing them with a new emphasis on the technical proficiency of thieves. This image of the criminal provided an outlet for ambivalent reflections on social and technological change, much as similar, high-security visions of the criminal have ever since. Hence, this essay both traces the origins of a neglected aspect of modern criminological thought and reconstructs the historical role of security provision in shaping visions of the criminal.