Explain illegality as a ground for judicial review under English law?

Under English law, illegality is one of the grounds for judicial review, which is the process by which a court reviews the lawfulness of executive or administrative action. Illegality as a ground for judicial review means that the decision being challenged must be in breach of a legal rule or provision. If a public authority has acted in a manner that is illegal, then the courts can intervene and declare the decision to be invalid. The principle of illegality in judicial review requires that public authorities act within the limits of their powers and comply with the relevant legal rules and provisions. If a decision has been made that is ultra vires (beyond the power) or contrary to a provision of law, then it may be found to be illegal and subject to judicial review. Examples of illegal decisions in the context of judicial review may include decisions that breach human rights, that are discriminatory, that breach the principles of natural justice, or that are contrary to statute law. It is important to note that the principle of illegality as a ground for judicial review applies only to public authorities, and not to private individuals or organizations. Additionally, a court may decline to grant relief on the ground of illegality if it would result in a disproportionate or unjust outcome.