Has the English Doctrine of Substantive Legitimate Expectation Evolved from Its Equitable Origins in Estoppel under the Influence of European Administrative Law?

This paper examines whether the English doctrine of substantive legitimate expectation has developed from its equitable roots in estoppel under the influence of European administrative law. It asks whether the similarities between English law and the law of the European Union reflect doctrinal borrowing, independent parallel development, or something in between. Using a doctrinal and comparative method, the paper analyses the leading English decisions alongside the case law of the Court of Justice of the European Union. Chapter 1 traces the affinity between legitimate expectation and equitable estoppel and explains why estoppel was rejected as a foundation in public law. Chapter 2 examines, in chronological order, the recognition of substantive protection in Coughlan and its refinement in Begbie, Bibi, Nadarajah, Finucane and later cases. Chapter 3 analyses the EU doctrine, its basis in legal certainty, its calibrated thresholds of protection and its remedies. Chapter 4 identifies the channels through which European law reached English doctrine and assesses how far it shaped the result. The paper argues that European influence on English law was real but mediated. It entered principally through litigation arising within the Community legal order, most notably Hamble, and through comparative scholarship, and it shaped the method by which English courts test the justification for departing from an expectation. It did not supply the legal basis of the doctrine, which remains domestic and is now understood as an application of the ordinary grounds of judicial review. Substantive legitimate expectation is therefore best understood as a hybrid doctrine: domestic in foundation, but convergent with European law in its reasoning.