Barber Professor of Jurisprudence, The University of Birmingham
Lest we forget what was actually said in 1948, Lord Greene stated:
It is true to say that, if a decision on a competent matter is so unreasonable that no reasonable authority could ever have come to it, then the courts can interfere. That, I think, is quite right; but to prove a case of that kind would require something overwhelming … It is not what the court considers unreasonable, a different thing altogether. If it is what the court considers unreasonable, the court may very well have different views to that of a local authority on matters of high public policy of this kind. Some courts might think that no children ought to be admitted on Sundays at all, some courts might think the reverse, and all over the country I have no doubt on a thing of that sort honest and sincere people hold different views. The effect of the legislation is not to set up the court as an arbiter of the correctness of one view over another. It is the local authority that are set in that position and, provided they act, as they have acted, within the four corners of their jurisdiction, this court, in my opinion, cannot interfere.
Put like this, unreasonableness as a ground of review is a straightforward concept, based on sound constitutional principles and a useful longstop to deal with a residual category of patently bad decisions. It makes abundantly clear that the courts are to make a secondary decision, with the primary decision about the merits of the matter being left to public authorities. The problem is that in the ensuing years we have heaped too much onto the unreasonableness test — we have attempted to make it too sophisticated, and we have used it...