- John StantonJohn StantonSenior Lecturer in Law, The City Law School, City, University of London
- and Craig PrescottCraig PrescottLecturer in Law, Bangor University
This chapter explores irrationality, the second ground for judicial review identified by Lord Diplock in Council of Civil Service Unions and Others v Minister for the Civil Service. It examines the meaning of this principle, its foundation upon the test of unreasonableness, and the approach that the courts have adopted since that case. Irrationality, and the notion of unreasonableness upon which it is based, is a particularly vague and ambiguous term, with a range of possible interpretations and meanings. This has meant that the courts have often considered judicial review claims, brought on the basis of irrationality, with varying degrees of caution, often employing the necessary tests with notable stringency. In part as a result of this, and in part also due to the increasing influence of European legal practices on the UK system, the test of proportionality has developed as a substantive ground for judicial review, often overlapping and sometimes conflicting with application of the irrationality doctrine.