1. where there is a legitimate expectation that an authority should bear in mind a previous policy, this can only be assessed with Wednesbury unreasonableness
2. where there is a procedural legitimate expectation, it must be complied with if there is an overriding reason to resile from it, this is assessed based on fairness
3. where there is a substantive legitimate expectation, the court can decide whether the frustration amounted to an abused of power, assessing this based on fairness against any overriding interest