Much work undertaken by the police is not strictly related to matters of criminality. Maurice Punch was one of the first scholars to document the fact that a lot of police work has nothing to do with crime, and instead, relates to welfare matters, calls for concern, or helping other organisations go about their own businesses (Punch 1979). As noted in the previous chapter, the dominance of non-crime matters remains an issue, with the UK College of Policing identifying that 84% of calls to police are non-crime related (College of Policing 2015). Most of this work is largely undocumented. The fact that police have had to deal with social issues falling through the gap of other services' remit (a point which we address later) has led police to take on the functions of a 'secret social service'. Through that work, the interaction of police with vulnerability in non-criminal encounters has become normalised. Understanding this work with vulnerability requires an understanding of how vulnerability is defined and measured, in public health, according to social determinants of health (