Irrationality and proportionality

Administrative decisions must meet a minimum threshold of rationality. Under Wednesbury unreasonableness, a decision is only reviewable if 'so unreasonable that no reasonable authority could ever have come to it'—an exceptionally high bar encoding judicial deference. Proportionality, imported via the Human Rights Act 1998, applies structured analysis: (1) legitimate aim, (2) suitability/rational connection, (3) necessity/less restrictive means, (4) fair balance between benefit and burden. Where Convention rights are engaged, proportionality displaces Wednesbury. The rationale: while Wednesbury respects democratic decision-making and the separation of powers, proportionality ensures fundamental rights receive meaningful protection through transparent, staged reasoning that compels public authorities to justify interferences.

Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223: Lord Greene MR established the tripartite test—relevant considerations, improper purpose, and decisions 'so absurd that no sensible person could ever dream that it lay within the powers of the authority.' This set the deferential standard that dominated for decades.

Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374: Lord Diplock formalised irrationality as a ground of review, defining it as decisions 'so outrageous in defiance of logic or accepted moral standards' that no sensible person could reach them. Crucial for establishing the modern threefold classification.

R (Daly) v Secretary of State for the Home Department [2001] UKHL 26: Lord Steyn contrasted proportionality with Wednesbury—proportionality requires courts to 'assess the balance which the decision maker has struck, not merely whether it is within the range of rational or reasonable decisions.' Watershed case distinguishing the tests' intensity.

Pham v Secretary of State for the Home Department [2015] UKSC 19: Lord Mance suggested common law proportionality could apply to fundamental rights even absent the HRA. Signals potential expansion beyond Convention rights, though no clear majority emerged.

Courts first identify which test governs: proportionality if a Convention right is engaged (or EU law applies); Wednesbury otherwise. For proportionality, work through four stages sequentially—identify the legitimate aim, test rational connection, examine whether less intrusive means exist, then balance competing interests. Evidence matters: what alternatives were considered? What would their impact be? For Wednesbury, apply holistic assessment—could any reasonable decision-maker have reached this conclusion? Look for logical flaws, bad faith, or gross disproportion. Both tests vary intensity with context: high scrutiny for personal liberty, substantial deference for national security or resource allocation. Courts calibrate through the 'discretionary area of judgment' (proportionality) or 'anxious scrutiny' (Wednesbury). The reviewing court asks 'is this justified?' not 'would we decide differently?'

Misstating Wednesbury's threshold: Students write 'unreasonable' when the test requires 'so unreasonable that no reasonable authority could ever have come to it'—precision matters. Assuming proportionality always applies: It governs only where Convention rights, EU law, or (possibly) fundamental common law rights are engaged—Wednesbury remains the default. Conflating proportionality stages: Each stage is distinct—suitability asks if the measure can achieve its aim; necessity asks if less restrictive means exist. Students often merge these or skip necessity entirely. Ignoring deference: Neither test applies mechanically—always discuss how subject-matter affects intensity of review.