This book, first published in 1965, describes the British penal system as it existed in the 1960s. It describes how the system defined, accounted for, and disposed of offenders. As an early work in criminology, it focuses on differences between, and changes in, the views held by legislators, lawyers, philosophers, and the man in the street on the topic of crime and punishment. Walker is interested in the extent to which their views reflect the facts established and the theories propounded by psychologists, anthropologists, and sociologists.

The confusion between criminologists and penal reformers was initially encouraged by criminologists themselves, many of whom were penal reformers. Strictly speaking, penal reform, according to Walker, was a spare-time occupation for criminologists, just as canvassing for votes is an ancillary task for political scientists. The difference is that the criminologist's spare-time occupation is more likely to take a moral form, and when it does so it is more likely to interfere with what should be purely criminological thoughts.

The machinery of justice involves the interaction of human beings in their roles of victim, offender, policeman, judge, supervisor, or custodian, and there must be a place for human sympathy in the understanding, and still more in the treatment, of individual offenders. This book is concerned with the efficiency of the system as a means to these ends. One of the main reasons why penal institutions have continued to develop more slowly than other social services is that they are a constant battlefield between emotions and prejudices. This is a great empirical study; against which the policy-maker and criminologist can measure progress or regression in British criminals and punishments.