This chapter presents the story of how proportionality became a core concept in English public law. This is a story of continuity and change. It is only since its connection to European law during the 1980s that proportionality acquired conceptual autonomy and was distinguished from the common law concept of reasonableness. While its application in domestic judicial review was rejected during the 1990s, the promoters of proportionality sought continuity between the common law and European human rights standards, among them proportionality. Since the incorporation of the convention in the domestic sphere, proportionality applies as a different head of review from irrationality. As a prong-structured test, it is very akin to the global proportionality model and it involves a significant extension of judicial powers. Still, the doctrine of deference ensures that the role of courts remains different from the one ascribed to the primary decision-makers.

In this chapter, I argue that proportionality has represented a fusion of substance and form that is strange to the game-like nature of the common law. It has embodied a method of review, and a way of legal thinking more generally, situated in diametrical opposition to Diceyan analytical positivism. Precisely due to its anti-Diceyan meaning, proportionality has been promoted as a principle that could establish coherence in English public law through the recognition of minimum substantive values. By using proportionality language, English lawyers have sought a little bit of myth and ritual in judicial review. Hence, the spread of proportionality in English public law should be read against the background of the rise of common law constitutionalism. In this respect, the HRA officialised and enhanced more subtle and progressive cultural transformations. The spill-over dynamic of proportionality expresses the continuing search for rationalism and myth in the ongoing construction of English public law.