# Judicial review grounds: illegality, irrationality, and procedural fairness

> **Key takeaway:** GCHQ map: illegality / irrationality (Wednesbury) / procedural impropriety (fairness + bias — Porter v Magill). Plus legitimate expectation and HRA s.6. Remedies discretionary. Permission stage is separate (see companion note).

- **Jurisdiction:** England & Wales
- **Practice area:** Public Law
- **Last reviewed:** 2026-08-04
- **Interactive page:** https://kttclegal.info/library/notes/PublicLaw/judicial-review-grounds
- **Keywords:** judicial review, illegality, irrationality, Wednesbury, procedural fairness, GCHQ, Porter v Magill, legitimate expectation, public law

## What is this about?

Beyond the permission filter, a judicial review claim must establish a recognised public-law ground. The classic tripartite organisation — illegality, irrationality, and procedural impropriety — from Council of Civil Service Unions v Minister for the Civil Service (the GCHQ case) remains the standard map, supplemented by legitimate expectation and human-rights review under the HRA 1998.

## What is the core rule?

A public-law decision may be quashed or otherwise remedied where the decision-maker acted illegally (misdirected in law, acted ultra vires, or failed to take account of relevant considerations / took account of irrelevancies), irrationally (Wednesbury unreasonableness in its modern intensity-variable form), or with procedural unfairness (breach of natural justice: fair hearing and rule against bias), or in breach of a legitimate expectation, or incompatibly with Convention rights where HRA s.6 applies. Remedies are discretionary.

## What are the elements or test?

1. Illegality: did the decision-maker correctly understand and apply the law; stay within powers; consider mandatory relevant factors and ignore forbidden irrelevancies (Padfield; Tameside)?
2. Irrationality: is the decision beyond the range of reasonable responses (Wednesbury), noting context-sensitive intensity of review?
3. Procedural fairness: bias (actual or apparent — Porter v Magill) or unfair process (notice, opportunity to make representations) given the statutory scheme and fairness requirements?
4. Legitimate expectation: clear promise or established practice; can the public body resile, and with what fairness/justification analysis?
5. HRA: is the body a public authority (s.6) and has it acted incompatibly with a Convention right? Apply proportionality where engaged

## Which authorities matter?

- **Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374** — Lord Diplock's classic threefold classification: illegality, irrationality, procedural impropriety.
- **Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223** — Foundational irrationality / unreasonableness standard, refined by later intensity-of-review case law.
- **Porter v Magill [2001] UKHL 67, [2002] 2 AC 357** — Apparent bias test: whether a fair-minded and informed observer would conclude there was a real possibility of bias.
- **R v Secretary of State for the Home Department, ex p Doody [1994] 1 AC 531** — Procedural fairness content depends on context; often includes the right to make representations informed by the gist of the case.

## How does this apply in practice?

Pair this note with the corpus entry on the judicial review permission stage for procedure. Ouster clauses, time limits (CPR 54), and standing are related procedural topics. Not every unfair outcome is a public-law error — merits review is not the default. Always identify the power source and the decision-maker's statutory purpose.

## What are common pitfalls?

- Re-arguing the merits under the label of irrationality without meeting the high threshold
- Pleading fairness in the abstract without tying it to the statutory scheme and facts (Doody)
- Ignoring that remedies are discretionary even if a ground is made out
- Missing HRA proportionality analysis where Convention rights are in play and treating everything as pure Wednesbury

## When would a practitioner use this?

Use when settling grounds of claim, advising on prospects after permission, or drafting summary grounds of resistance.

## Quick reference

GCHQ map: illegality / irrationality (Wednesbury) / procedural impropriety (fairness + bias — Porter v Magill). Plus legitimate expectation and HRA s.6. Remedies discretionary. Permission stage is separate (see companion note).

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*Reference material from [KTTC Legal](https://kttclegal.info/), not legal advice. Work product supports instructing solicitors and barristers under their supervision. England & Wales.*