What is the difference between irrationality and illegality in judicial review?

Illegality is about a body acting outside or contrary to the legal powers it was given, such as pursuing an improper purpose or taking irrelevant considerations into account. Irrationality (Wednesbury unreasonableness) accepts the body had power to act but challenges the outcome as so unreasonable no rational decision-maker could have reached it. The distinction matters because they require different arguments and attract different levels of judicial scrutiny.

Does a claimant need to exhaust alternative remedies before seeking judicial review?

Generally yes. The Administrative Court expects claimants to pursue any adequate alternative remedy first, such as a statutory right of appeal. The court has discretion to refuse permission if an adequate alternative exists and there is no good reason why it was not used.

How does proportionality differ from Wednesbury unreasonableness?

Wednesbury asks only whether the decision was so unreasonable that no reasonable authority could have made it, which is a very high bar. Proportionality requires a structured four-stage analysis: legitimate aim, rational connection, necessity, and fair balance. Proportionality is the standard in HRA cases and results in more intensive judicial scrutiny of the decision.

Can a private company ever be subject to judicial review?

Yes, under the Datafin principle, a private body is amenable to JR if it exercises a public function that would otherwise be performed by government. Courts look at the source of the power and the nature of the function. Pure contractual relationships between private parties are not reviewable.

What happens if a claimant wins on the grounds but the court refuses a remedy?

Remedies in judicial review are always discretionary, so a successful ground does not guarantee relief. The court may decline to grant an order if the outcome would inevitably have been the same, if the claimant delayed unreasonably, or if granting relief would cause disproportionate hardship to third parties. Always address this point in an exam answer.

Public Law

Judicial Review Step by Step: Public Law Revision Guide

A structured walkthrough of every JR stage, from standing to remedies, with the cases and tests examiners actually want.

Quill

Caselaw editorial desk · 16 June 2026

Judicial review questions are won or lost on structure. Get the sequence right and the marks follow naturally. Miss a stage or blur the grounds together, and even solid knowledge of the cases won't save you.

This guide walks through every step in the order you should address it in an exam answer, with the tests, the cases, and the framing that examiners reward.

Step 1: Is This a Public Law Matter?

Before you touch standing or grounds, confirm that judicial review is the right vehicle at all. JR is a mechanism for controlling the exercise of public functions. The Administrative Court will refuse to hear a challenge if the defendant is a purely private body.

The test comes from R v Panel on Take-overs and Mergers, ex parte Datafin [1987] QB 815. The Court of Appeal held that a body may be subject to JR if it exercises a public function, even without a statutory basis, looking at the source of the power and the nature of the function. The Panel itself had no statutory footing, yet its decisions were reviewable because it was woven into a system of public regulation.

Contrast that with R v Disciplinary Committee of the Jockey Club, ex parte Aga Khan [1993] 1 WLR 909, where the Jockey Club was held to be a purely private body. Its power over the applicant derived from contract, not from any public framework. The court declined jurisdiction.

In an exam, ask yourself:

Is the decision-maker a government minister, local authority, statutory tribunal, or other obviously public body? If yes, move on.
If it is a private or hybrid body, apply Datafin: source of power and nature of function.
Does the applicant have a private law alternative (contract, tort)? If a purely private law route exists, JR may be refused as an abuse of process.

Step 2: Procedural Requirements

JR is governed by Part 54 of the Civil Procedure Rules. You need to know the basics even if your exam is substantive rather than procedural, because a problem question may require you to flag these.

Permission stage. The applicant must obtain permission from the Administrative Court before the full hearing proceeds. This filters out hopeless claims.

Time limit. Claims must be brought promptly and in any event within three months of the date the grounds arose (CPR 54.5). Some statutory contexts impose shorter limits. "Promptly" is a real requirement and can bite even within the three months.

Pre-action protocol. There is a formal pre-action protocol for judicial review. The claimant should send a letter before claim, and the defendant should respond within 14 days (21 days for complex cases). Failure to follow the protocol can affect costs.

Ouster clauses. These are legislative attempts to exclude judicial review. Standard ouster clauses are read very narrowly by the courts. Anisminic Ltd v Foreign Compensation Commission [1969] 2 AC 147 is the foundational authority: a clause saying a determination "shall not be called in question" in any court did not protect a determination that was a nullity due to jurisdictional error. The principle that Parliament cannot wholly oust judicial supervision of legality connects directly to constitutional fundamentals going back to *Entick v Carrington*, where the court refused to accept executive action without clear legal authority.

Step 3: Standing (Locus Standi)

Section 31(3) of the Senior Courts Act 1981 requires the applicant to have "sufficient interest" in the matter. This is deliberately broad.

The leading case is R v Inland Revenue Commissioners, ex parte National Federation of Self-Employed and Small Businesses Ltd [1982] AC 617 (the Fleet Street Casuals case). The House of Lords confirmed that standing is not a preliminary technical hurdle to be decided in isolation; it is assessed in light of the whole legal and factual context, including the merits of the claim.

Public interest standing is well established. Pressure groups and representative bodies can often establish sufficient interest. R v Secretary of State for Foreign Affairs, ex parte World Development Movement Ltd [1995] 1 WLR 386 is the classic example: an NGO had standing to challenge UK aid payments to the Pergau Dam project, given the organisation's expertise and the absence of any more obvious challenger.

In a problem question, do not just say the applicant has standing. Identify why, by reference to the statutory test and the relevant authorities.

Step 4: The Grounds of Review

This is the heart of most JR exam questions. The orthodox categorisation from Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374 (the GCHQ case) divides the grounds into three: illegality, irrationality, and procedural impropriety. Lord Diplock also suggested legitimate expectation as a developing head. Human rights now adds a fourth major layer.

Illegality

The decision-maker must understand and act within the law that gives them power. Several sub-categories appear regularly.

Ultra vires (simple). The body has acted outside the four corners of its statutory power. Check the enabling Act carefully.

Wrongful delegation. A body may not delegate a power unless the statute authorises delegation. Lavender & Son Ltd v Minister of Housing and Local Government [1970] 1 WLR 1231 is the clearest exam-ready example: the Minister fettered his discretion by treating himself as bound to follow the policy of another minister, amounting to unlawful delegation of his own decision-making.

Fettering discretion. A public body must not apply a rigid policy without genuine consideration of individual circumstances. It can adopt a policy, but must always be willing to consider exceptions.

Improper purpose. Power must be exercised for the purpose Parliament intended. *Roberts v Hopwood* is the textbook case: Poplar Borough Council used its statutory wage-setting power to pay wages well above market rates, partly out of socialist ideology. The House of Lords held the council had pursued an improper purpose, acting as "model employers" rather than stewarding public funds as Parliament intended.

Relevant and irrelevant considerations. A decision-maker must take into account what the statute requires and ignore what it does not permit. Padfield v Minister of Agriculture [1968] AC 997 is essential here.

Irrationality (Wednesbury Unreasonableness)

Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223 set the test: a decision is unlawful if it is so unreasonable that no reasonable authority could ever have come to it. Lord Greene MR's judgment is much cited, but the real threshold is a high one. Courts are not substituting their own view.

The threshold becomes proportionality when Convention rights are engaged (see below). In purely domestic judicial review without a HRA angle, Wednesbury remains the standard, though Lord Cooke in R v Secretary of State for the Home Department, ex parte Daly [2001] UKHL 26 questioned whether the Wednesbury label was helpful and suggested a more structured approach was developing.

In a problem question, Wednesbury irrationality is best raised when a decision is objectively outrageous or when the decision-maker has clearly shut their eyes to obvious facts. Mere disagreement with the merits is not enough.

Procedural Impropriety

This covers two separate things, and students frequently conflate them.

Breach of statutory procedure. Where Parliament has laid down a procedure, failure to follow it may render the decision unlawful. Whether it does depends on whether the requirement is mandatory or directory. Agricultural, Horticultural and Forestry Industry Training Board v Aylesbury Mushrooms Ltd [1972] 1 WLR 190 illustrates the mandatory/directory distinction.

Common law procedural fairness (natural justice). This has two limbs:

The right to a fair hearing (audi alteram partem): the person affected must have the opportunity to know the case against them and respond.
The rule against bias (nemo iudex in causa sua): the decision-maker must not have a personal or financial interest in the outcome. R v Gough [1993] AC 646 and Porter v Magill [2001] UKHL 67 are the key bias cases; the current test asks whether a fair-minded and informed observer would conclude there was a real possibility of bias.

The content of the duty of fairness is variable. Council of Civil Service Unions v Minister for Civil Service [1985] AC 374 confirmed that legitimate expectations can be procedural (an expectation of being consulted before a decision is made) or substantive.

For the procedural dimension, *Osborn v Parole Board* is an excellent modern authority. The Supreme Court held that the Parole Board's failure to hold oral hearings in certain cases breached the common law duty of procedural fairness, and also considered Article 5(4) ECHR. Lord Reed's judgment is a model of how the common law and Convention rights interact in practice. The case is good exam ammunition because it shows the courts pushing common law procedural rights without needing to collapse everything into HRA analysis.

Human Rights Act 1998

Where a public authority acts incompatibly with a Convention right, section 6 HRA makes that act unlawful in itself. This operates as a distinct, fourth ground in any HRA-enabled JR.

The standard of review shifts. Instead of Wednesbury, the court applies proportionality: whether the interference with the right pursues a legitimate aim, is rationally connected to that aim, is no more than necessary, and strikes a fair balance. De Freitas v Permanent Secretary of Ministry of Agriculture [1999] 1 AC 69 and Bank Mellat v HM Treasury (No 2) [2013] UKSC 39 set out the four-stage test now applied.

The margin of discretion the court allows the public authority varies with the nature of the right. Deference is greater in areas of social and economic policy, less so where the right is directly personal (say, Article 3 or Article 8 in a family context).

Step 5: Remedies

JR remedies are discretionary. Even a successful claimant can be refused relief.

The prerogative remedies are:

Quashing order (formerly certiorari): sets aside the unlawful decision. The most commonly sought remedy.
Mandatory order (formerly mandamus): compels the body to perform a public duty.
Prohibiting order (formerly prohibition): prevents a body from acting unlawfully in the future.

The court can also grant a declaration (stating the legal position without formal compulsion), an injunction, or damages (though damages are available in JR only where an independent cause of action exists, such as under the HRA or in tort).

When a quashing order is granted, the court can either remit the matter back to the original decision-maker or, less commonly, substitute its own decision if the matter is suitable for that.

Discretion to refuse relief. Even a well-founded claim can be refused if:

The claimant has delayed without good reason.
The outcome would inevitably have been the same.
The claimant has acquiesced in the unlawful act.
Granting relief would cause substantial hardship or prejudice third parties.

Always address discretion in a problem question, even briefly. It shows the examiner you understand that a successful ground does not automatically produce a remedy.

Putting It Together in an Exam

JR problem questions usually involve a statutory body, a controversial decision, and an aggrieved individual or organisation. Work through this sequence:

Public law matter? (Datafin if private/hybrid body.)
Procedural requirements met? (Time limit, permission, any ouster clause.)
Standing? (Sufficient interest under s.31 SCA 1981.)
Grounds: work through illegality, irrationality, procedural impropriety, and HRA systematically. Do not shotgun all four without analysis. Pick the ones the facts actually support.
Remedies: which order is appropriate, and is there any reason the court might refuse relief?

Do not spend equal time on each stage. If the facts clearly raise a procedural fairness issue, that is where your marks are. Identify the live questions and develop them; do not give a paragraph to a ground the facts do not engage.

For deeper reading on the constitutional foundations of public law and for drilling past exam questions, the Public Law topic hub is a good starting point, and working through past papers with model answers will sharpen your instincts for which grounds are live on a given set of facts.