More than three years have passed since the introduction of the so-called “no (substantial) difference” test in judicial review. By an amended s.31 Senior Courts Act 1981 (“SCA“),an application for judicial review should now be “book-ended” with an assessment of the extent to which the conduct complained of made a substantial difference to the outcome for the applicant. The court will consider the test first when deciding whether to grant permission for the application and secondly when deciding whether or not to grant relief.

The amendment marked a departure from the test of “inevitability” that previously applied at common law as the justification for refusing to grant relief. However, what emerges from a review of a number of recent decisions is that, when applying this test, courts are hesitant to speculate on what outcome would have been likely to arise had the conduct complained of not occurred. As a consequence, the no substantial difference test has not provided an easy escape mechanism for defendants seeking to resist judicial review claims.

The substantive test and its application


As a result of the reforms implemented by the amendments to s.31 SCA more than three years ago, the court will consider the “no difference” test when deciding whether to grant permission for a judicial review application (it may do so of its own motion, pers.31(2A) of the SCA, but must do so where the defendant requests this) and, in all cases that reach this stage, at the point of deciding whether or not to grant relief. If, on considering the test, it appears to the court to be highly likely that the outcome for the applicant would not have been substantially different, the court must refuse to grant leave or relief as the case may be. The court retains a limited discretion to allow leave for an application or relief on grounds of exceptional public interest. The introduction of the test marked a departure from the test of inevitability (whereby the court may refuse relief or refuse to grant permission if satisfied that it is inevitable that the outcome would have been no different) that previously applied at common law.

In considering whether the outcome for the applicant would have been substantially different if the conduct complained of had not occurred, be that at the permission stage or at the point of granting relief, courts have considered the materiality of the conduct in question to the decision while resisting engaging in speculation as to the impact of conduct.

(a) Materiality 

At both stages, courts have focused on the materiality of the conduct complained of to the outcome of the case. Unless the conduct complained of bears little significance to the outcome overall, the test will not be met, as there is a “high threshold for a finding that it is highly unlikely that the outcome for the applicant would not have been substantially different if the conduct complained of had not occurred“: R (on the application of B) v OIA [2018] EWHC 1971 (Admin)).

In R (on the application of Spitalfields Historic Trust Ltd) v Mayor of London [2016] EWHC 1006 (Admin), the court relied on s.31(2A) to decline relief in a challenge to a planning decision by the Mayor of London. The court accepted that it was “unfortunate” that the defendant’s report falsely gave the impression that the claimant’s letter had been addressed. However, it was “hard to see how the points taken by [the claimant] would have led to a different decision“, given that a number of the substantive points raised had nevertheless been considered at length in the report.

A similar approach was taken in R (on the application of B) v OIA where a former medical student (having been declared unfit to practise as a doctor by his former university) challenged a decision of the Office of the Independent Adjudicator (“OIA”). The OIA refused to re-open the Fitness to Practice proceedings as they considered the matter had been dealt with by separate breach of contract proceedings which had concluded in a strike out of the substantive claim. The court accepted that, for the purposes of s.31(2A), it was highly likely that the result would have been the same even if the OIA had found the complaint to be eligible, as it would nevertheless have decided that the university’s refusal to re-open its Fitness to Practise proceedings was reasonable and justified.

In R (on the application of Piffs Elm Ltd) v Tewkesbury BC [2016] EWHC 3248 (Admin), a developer sought judicial review of the local authority’s refusal of its planning application, on the basis that one of the reports relied on by the Planning Committee was undermined by the apprehended bias of the officer who prepared the report. In considering whether to grant permission, the court was not satisfied that it would be highly likely that the decision would have been the same without the planning officer’s involvement, as the report was relied on by the Planning Committee in weighing up of countervailing planning permission considerations about which “different people may come to different conclusions” and the exercise of “classic issues of planning judgment“. The original Planning Committee vote had also been close.

A number of decisions have shown the court’s willingness to construe the provisions narrowly, with the previous “inevitability” approach seemingly influencing the way in which judges tackle the application of the test. In R (on the application of Guerry), v London Borough of Hammersmith & Fulham [2018] EWHC 2899 (Admin) the test was applied to determine that a similar conclusion would not “necessarily” have been reached had the planning officer’s errors not been included and, without more, it could not be said that the outcome was highly likely to have not been substantially different. In Spitalfields, Gilbart J held that the decision on one of the points raised in the grounds of challenge “would inevitably have been the same” even if the particular matter had not been raised in the disputed report – the relevant ground failed on that basis. He reached this conclusion before considering s.31(2A), setting out the test and concluding simply that it was met.

Where the test is considered in the context of refusing relief, it is often expressed as an additional basis to fortify the court’s conclusions in the case: that is to say, the claim is dismissed following the court’s findings on the relevant facts and law, and the test is cited as an additional basis on which to denying the claimant relief: see e.g. R (on the application of Finney) v Welsh Ministers [2018] EWHC 3073 (Admin) and R (on the application of B) v OIA.

(b) Avoiding speculation

In a number of cases, courts have refused to find that the no substantial difference test has been met where doing so would have required the court to engage in speculation.

In R (on the application of Logan) v London Borough of Havering [2015] EWHC 3193 (Admin), Blake J emphasised that the assessment ought not to be based simply on “post-decision speculation by an individual decision maker“. He concluded that the provision was to be interpreted so as not to undermine the “efficacy of judicial review as an instrument to ensure that the rule of law applies to decision making by public authorities“. Mere speculation by a decision-maker (rather than relying on the materials in existence at the time of the decision) could have a chilling effect, “deterring claimants from bringing a case or the court from granting permission by a declaration“. This was not something that Blake J was prepared to accept as Parliament’s intention – such a “draconian modification of constitutional principles” could not, in his view, be countenanced.

To similar effect, in Guerry the court quashed a decision to award planning permission after Councillors were significantly misled by a report on the issue of light distribution. The Planning Court dismissed as “a matter of speculation” consideration of whether the Councillors may have requested further information and imposed more revisions to the design had they been made aware of the full extent of the light distribution issue. In the court’s view, it was equally possible that the Councillors might not have done this. In R (on the application of Christchurch Borough Council) v SSFHCLG [2018] EWHC 2126 (Admin) the Secretary of State used an express Henry VIII power (which is a power to create secondary legislation that amends or repeals provisions of primary legislation) to create a single tier of local government across Dorset, Bournemouth and Poole. The court found that the disputed regulations were intra vires and that there was “no vice of retrospectivity“. The Claimant suggested that if matters had proceeded differently, the proposal or the process used to consider its merits would not necessarily have been the same. This was rejected by the court as mere speculation: the court was satisfied that it was highly likely that the outcome would not have been substantially different.


There was consternation at the introduction of the reforms to s.31 SCA 1981 with fears that the no substantial difference test would intrude further on the court’s discretion to grant relief or indeed to hear cases at all by limiting grants of permission for judicial review.

However, in many cases the application of the test has simply reflected the general centre of gravity of the judgment on the substantive issues. In R (on the application of B) the claim was dismissed on the grounds that the matter had in effect already been decided in earlier proceedings – the s.31(2A) test was then said to have been satisfied; in Guerry the relevant report was deemed to be significantly misleading – the s.31(2A) test was then said not to have been satisfied; in R (on the application of Langton) v SSEFRA [2018] EWHC 2190 (Admin) the claim was dismissed on the grounds that the disputed guidance and licensing decisions were valid – the s.31(2A) test was said to have been satisfied.

Nevertheless, the amendments to s.31 SCA have introduced potential “safety valves” for defendants to seek to rely on at the beginning and end of the judicial review process. Procedurally, the court is now compelled to consider the matter when raised by the defendant at the permission stage. However, forcing the judge’s gaze alone will not alter what she or he sees and the threshold to be applied remains high.


Andrew Lidbetter
Andrew Lidbetter
+44 20 7466 2066
Nusrat Zar
Nusrat Zar
+44 20 7466 2465
Jasveer Randhawa
Jasveer Randhawa
Of Counsel
+44 20 7466 2998