“The flexibility necessarily inherent [in the unreasonableness test] should not be sacrificed on the altar of legal certainty”. (Simon Brown LJ in R v IRC, ex p Unilever plc  STC 681 at paragraphs 694-695).
The Court has broad discretion when considering a decision’s reasonableness. The factors it will choose to consider (and the intensity of the scrutiny) will vary from case to case and will depend on the context. It is therefore not possible to provide an exhaustive list of the factors that the Court will consider in all cases. Indeed, the Court themselves have said that the list of grounds that may be considered in determining whether a decision is unreasonable is “probably limitless”.
As a general guide, some of the Court’s considerations in decided cases are set out under the headings on the right.