This text is a critical study of the public/private law divide in the common law tradition. Professor Oliver's starting point is that special substantive duties of legality, fairness and rationality are imposed by the common law on bodies discharging public functions, but not always on bodies discharging what are considered 'private' functions. She questions the validity of the traditional dichotomy, and proposes new criteria for imposing such duties in accordance with underlying values, including the control of power and respect for the individual's autonomy and dignity. Written by a leading law academic, this is an important and original contribution to public law literature, providing an informed and considered overview for legal academics and students.