“[Is] the decision in question … one which a reasonable authority could reach[?]”In his view, such a formulation would still “give the administrator ample and rightful rein, consistently with the constitutional separation of powers”. Similarly he was a fan of the so-called "innominate" ground of review expressed by Lord Donaldson in the Guinness case: the standard being "whether something had gone wrong of a nature and degree which required the intervention of the court". Lord Donaldson's formulation mirrored his own expression of the concept of substantive fairness in the Thames Valley case, which he described as “a legitimate ground of judicial review, shading into but not identical with unreasonableness”. Sir Robin welcomed this as a "refreshing and healthy move away ... from the more formalistic constraints once orthodox" and suggested that:
[J]udges are accepting that they have a responsibility to do practical justice in administrative law as in other fields. Ample room for respect for administrative discretion remains.And he was a strong champion of fairness. The translation of the motto found on his personal coat of arms says: "To speak in favour of fairness". His judgments expressed the need for the courts to ensure both procedural and substantive fairness when exercising their supervisory jurisdiction. I have already mentioned to his adoption of the principle of substantive fairness and the closely aligned simple expression of the reasonableness standard. To this one can add his strengthening of the principle of procedural fairness in Daganaysi, along with the genesis of the mistake of fact doctrine in the same case. He also often indicated the importance of consultation in ensuring the delivery of natural justice and procedural fairness, notably in administrative decisions relating to Maori and more generally with the populace at large. Again, Lord Cooke was not one to be tied down by legal niceties or formalistic definitions of fairness. He commended the word of Lord Justice Lawton in the Maxwell case:
"From time to time … lawyers and judges have tried to define what constitutes fairness. Like defining an elephant, it is not easy to do, although fairness in practice has the elephantine quality of being easy to recognise."His scholarship and adjudication endeavoured to achieve real justice in individual cases. He was no doubt pleased to see the rejection of legal formalism by our courts continue beyond his retirement from the Court of Appeal. The desire for individual justice also came with an acceptance of discretion in administrative law. Sir Robin once noted that when he was writing his PhD he was "quite well-deposed towards discretion" – in contradistinction to famous administrative law names such as Dicey and Sir William Wade. He went on to say that almost a quarter of a century on the bench had "warmed [his] feelings to something approaching affection for it". He understood the need for both administrative and judicial discretion in this area. However, he accepted that both were subject to limits, but limits which varied according to the subject-matter and surrounding statutory context. He queried whether administrative law might be better renamed "the law of public discretions". His acceptance of the role of discretion and rejection of rigid rules imbued his adjudication and scholarship. His formulation of the grounds of review provided for appropriate discretion. He embraced the discretionary approach to remedies in judicial review, rejecting the strait-jacket presented by the previous "void" – "voidable" distinction. He championed a discretionary approach to procedural matters, such as the question of standing. Discretion was a paramount vehicle to achieving individual justice. Lord Cooke's contribution to New Zealand – and Commonwealth – administrative law was massive. It is marked particularly by its pursuit of simplicity and fairness. We have lost one of our greatest figures in administrative law. Ka hinga te totara o te wao nui a tane. But he will not be forgotten. His legacy in this area will endure.