Explain legitimate expectation as a ground for judicial review under English law?

Under English law, the principle of legitimate expectation is a ground for judicial review, which is the process by which a court reviews the lawfulness of executive or administrative action. Legitimate expectation is a principle of administrative law that requires public authorities to act in accordance with representations that they have made to individuals or groups. A legitimate expectation arises where a public authority has made a clear and unambiguous representation to an individual or group that it will follow a particular procedure, grant a particular benefit, or refrain from taking a particular action. If the public authority then acts in a way that is inconsistent with that representation, it may be subject to judicial review on the ground of legitimate expectation. There are two types of legitimate expectation: procedural legitimate expectation and substantive legitimate expectation. A procedural legitimate expectation arises where a public authority has made a representation that it will follow a particular procedure when making a decision. If the public authority fails to follow that procedure, the individual or group may have a right to have the decision quashed and to have the matter reconsidered in accordance with the promised procedure. A substantive legitimate expectation arises where a public authority has made a representation that it will grant a particular benefit, such as a renewal of a license or the continuation of a policy, or that it will refrain from taking a particular action, such as the closure of a particular facility. If the public authority acts in a way that is inconsistent with that representation, the individual or group may have a right to have the decision quashed and to have the matter reconsidered in accordance with the promised benefit or restraint.