29 The test of manifest (Wednesbury) unreasonableness has been stated in various ways. In Bromley London Borough Council v Greater London Council [1983] 1 AC 768 at 821, Lord Diplock said that the test was whether the decision: "looked at objectively, [was] so devoid of any plausible justification that no reasonable body or persons could have reached [it]". In Council of Civil Service Unions v Minister for the Civil Service [1985] 1 AC 374 at 410, Lord Diplock said that the decision must be "so outrageous in its defiance of logic or of accepted moral standards that no sensible person who had applied his mind to the question to be decided could have arrived at it". It has been said that "The test is stringent… The decision must amount to an abuse of power (Attorney-General (NSW) v Quin (1990) 170 CLR 1 at 36) or be so devoid of plausible justification that no reasonable person could have taken that course (Minister for Immigration and Ethnic Affairs v Teoh (1995) 183 CLR 273 at 290)": Weal v Bathurst City Council (2000) 111 LGERA 181 (NSWCA) at 188 [27]; Wyong Shire Council v MCC Energy Pty Ltd (2005) 139 LGERA 296 (NSWCA) at 312 [79]. In Woolworths Limited v Pallas Newco Pty Limited (2004) 61 NSWLR 707 at 725 [91], Spigelman CJ (with whom Mason P agreed) said that the test was whether a decision "was so plainly incorrect as to satisfy the stringent requirements of the Wednesbury unreasonableness test". In Murrumbidgee Groundwater Preservation Association Inc v Minister for Natural Resources (2005) 138 LGERA 11 at 45 [129], Spigelman CJ (with whom Beazley and Tobias JJA agreed) said: "Perhaps the most appropriate formulation is whether the decision is 'illogical, irrational or lacking a basis in findings or inferences of fact supported on logical grounds': Re Minister for Immigration and Multicultural Affairs; Ex parte Applicant S20/2002 (2003) 77 ALJR 1165 at [52] and [37], [173]; see also Minister for Immigration and Multicultural and Indigenous Affairs v SGLB (2004) 78 ALJR 992 at [38]'. The formulation in Murrumbidgee was quoted in Westfield Management Limited v Perpetual Trustee Company Limited [2006] NSWCA 245 at [71] by Tobias JA. In Andary v Minister for Immigration and Multicultural Affairs [2003] FCAFC 211 at [10], the Full Court of the Federal Court thought there was a great deal of wisdom and practicality Lord Cooke of Thorndon's observations in R v Chief Constable of Sussex, Ex parte International Trader's Ferry Ltd [1998] 3 WLR 1260. His Lordship said in that case at 1228-1289:
It seems to me unfortunate that Wednesbury and some Wednesbury phrases have become established incantations in the Courts of United Kingdom and beyond. Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223, an apparently briefly-considered case, might well not be decided the same way today; and the judgment of Lord Greene M.R. twice uses (at pp 230 and 234) the tautologous formula ' so unreasonable that no reasonable authority could ever have come to it '. Yet judges are entirely accustomed to respecting the proper scope of administrative discretions. In my respectful opinion they do not need to be warned off the course by admonitory circumlocutions. When, in Secretary of State for Eduction and Science v Tameside Metropolitan Borough Council [1997] AC 1014, the precise meaning of ' unreasonably ' in an administrative context was crucial to the decision, the five speeches in the House of Lords, the three judgments in the Court of Appeal and the two judgments in the Divisional Court all succeeded in avoiding needless complexity. The simple test used throughout was whether the decision in question was one which a reasonable authority could reach. The converse was described by Lord Diplock, at p 1064 as ' conduct which no sensible authority acting with due appreciation of its responsibilities would have decided to adopt '. These unexaggerated criteria give the administrator ample and rightful rein, consistently with the constitutional separation of powers.