This thesis examines the way in which the doctrine of legitimate or reasonable expectations has developed in the common law of England and Australia. The examination aims to show the role of expectations in the modern re-balancing of interests between the citizen and the Crown or government. The concept of expectations is examined both as it has developed into a doctrine in its own right, and as a theme which is shaping the development of other existing doctrines. i A preoccupation throughout the thesis is the way in which expectations are causing heightened standards of conduct from both the Crown or government when dealing with individual citizens, and from individual citizens dealing inter se. The traditional operation of many legal doctrines which have applied preferentially in favour of the Crown or government is examined. This tradition is exemplified in a limited way by the law relating to claims against the government, the principle of immunity of the Crown from statute, the law of estoppel and the law of restitution. Examination of the progressive reduction of such preferences exposes the significant role of the expectations concept in the re-balancing of the citizen-State relationship. The particular role and meaning of the "Crown", the "government" and the "administration" is central to the understanding of the preferential operation of certain doctrines. Consideration is given to the historic and current meaning of these institutions, their responsibilities and their relationship with the individual citizen. This examination helps to determine whether the role of such institutions has so changed as to justify the development of doctrines to accommodate new expectations. The development of the concept of expectations is examined in both public (or administrative) law and private law. In each sphere, the concept has developed differently, and distinct differences also emerge in the development of the concept by the English and Australian judiciary. These differences reveal important perceptions about the role of the courts in regulating governmental action, the capacity of the courts to develop new or existing legal principles, and the recognition changed expectations of individual citizens will be given in legal doctrine. In public law, the concept of expectations has developed into a distinct legal doctrine. The scope of the doctrine is examined, in particular whether it enables a substantive or merely procedural remedy to be granted where a person's expectation is disappointed. Barriers to the expansion of the scope of the doctrine are critically examined, and a solution proposed to enable the expansion of the doctrine without offence to the prineiples restricting such expansion. Additional issues of locus standi and the bodies subject to the doctrine oflegitimate expectations are reviewed, as well as the scope of the doctrine in European Community law. In private law, the concept of expectations is not an independent doctrine. It nevertheless discloses a powerful capacity to shape the development of existing doctrines so that they protect modern expectations. Unlike expectations in public law, private law doctrines can substantively protect legitimate or reasonable expectations. Consideration is given to the way in which developments in private law can or should influence developments in public law, so that the doctrine of legitimate expectations develops coherently and uniformly. Structure is given to expectations in private law by isolating the main usages of the concept. The usages of the concept are exemplifed by consideration of expectations in the law of contract, tort and equity. Use of the concept of expectations by the judiciary to expand the scope of existing doctrines and to develop new doctrines raises the question of the proper role of the judiciary in the review of governmental action. The propriety of judicial concern with governmental action and judicial law-making are considered. Other means of protecting expectations are examined, including constitutional guarantees, the Rule of Law, the theory of ministerial responsibility and fundamental principles of right and reason. . The close alignment of the expectations concept with the recent resurgence in legal reasoning of the language of morality is examined. Consideration of the place of the terminology of morality in the shaping of the law reveals a notable judicial development of the concept of the Crown or government as moral exemplar. This, combined with the expectations concept has carved out a large role for the place of legitimate or reasonable expectations in the law of England and Australia.