Under the new requirements, the High Court must now refuse to provide a remedy where it appears “highly likely” that the outcome would not have been substantially different had the relevant conduct not occurred – unless exceptional public interest applies. 

In addition, when considering whether to grant permission to make an application for judicial review, the High Court may (and must if the defendant asks it to) consider whether the outcome would have been substantially different had the relevant conduct not occurred. The Court must refuse permission if it appears highly likely that it would not have been – again, unless exceptional public interest applies.

The above requirements amend and put into statute the existing discretion of the Courts to refuse permission or to provide remedies.


An intervener is a party who voluntarily applies to become involved in a judicial review in the High Court or Court of Appeal. Under the new requirements, unless exceptional circumstances apply, the presumption is that such interveners should bear their own costs. 

The Court must order the intervener to pay a party’s costs resulting from the intervention if one of the following apply (again save in exceptional circumstances):

  • the intervener has essentially acted as the sole or principal applicant, defendant, appellant or respondent or has behaved unreasonably; or
  • as a whole, the intervener’s evidence and representations have not been of significant assistance to the court or a significant part of such evidence and representations relate to matters which are not necessary for the courts to consider.

Careful thought is required by potential interveners as to the risk of incurring costs before proceeding.


Finally, the challenge periods for certain planning related challenges (including challenges to development consent orders) have been harmonised and now commence from the date after the date of the decision.