The Long Arm of the Law

In one sense, Policing is a simple task. Police officers put themselves at the point of conflict, real or potential, and endeavour to keep or restore the peace. In order to to able to do so, they need not so much a strong arm (although that may be necessary on occasion), or an intimate knowledge of the law, as a ready tongue and a large measure of common sense.
Police officers may enforce the law; but it could be argued that their true purpose is, far more often to explain the rules.

Police and Policing: An Introduction By Peter Villiers