The doctrine of legitimate expectation was first developed in English law as a ground of judicial review in administrative law to protect a procedural or substantive interest when a public authority rescinds from a representation made to a person. It is based on the principles of natural justice and fairness, and seeks to prevent authorities from abusing power. The courts of the United Kingdom have recognized both procedural and substantive legitimate expectations. A procedural legitimate expectation rests on the presumption that a public authority will follow a certain procedure in advance of a decision being taken, while a substantive legitimate expectation arises where an authority makes a lawful representation that an individual will receive or continue to receive some kind of substantive benefit. In determining a claim for an alleged breach of a legitimate expectation, a court will deliberate over three key considerations: whether a legitimate expectation has arisen; whether it would be unlawful for the authority to frustrate such an expectation; and if it is found that the authority has done so, what remedies are available to the aggrieved person. Procedural legitimate expectations have been recognized in a number of common law jurisdictions. In contrast, notwithstanding their acceptance and protection in the UK, substantive legitimate expectations have not been universally recognized. For instance, they have been given effect in Singapore but not in Australia. Introduction Origins and basis of the doctrine Since its inception, the doctrine of legitimate expectation has been viewed as an offshoot of natural justice. The duty to act fairly is a core tenet of administrative law and a predominant feature in the application of the rules of natural justice. With each individual's entitlement to natural justice and fairness, legitimate expectation reinforces the duty of public bodies to act fairly. It is this protection of fairness that made way for the courts' acknowledgement of legitimate expectations. In their elaboration of the doctrine, courts of the United Kingdom adopted other key aspects of judicial review such as Wednesbury unreasonableness, fairness, and abuse of power to justify the existence and the protection of legitimate expectations. The term legitimate expectation was first used in the case of Schmidt v Secretary of State for Home Affairs (1968), but was not applied on the facts. Subsequently, in O'Reilly v Mackman (1983) the doctrine of legitimate expectation was recognized as part of judicial review in public law, allowing individuals to challenge the