In the matter of an application by Geraldine Finucane for Judicial Review (Northern Ireland) (2019) UKSC 7 considers substantive legitimate expectation from paragraph 55. Lord Kerr on behalf of the Supreme Court concluded:-
“62. From these authorities it can be deduced that where a clear and unambiguous undertaking has been made, the authority giving the undertaking will not be allowed to depart from it unless it is shown that it is fair to do so. The court is the arbiter of fairness in this context. And a matter sounding on the question of fairness is whether the alteration in policy frustrates any reliance which the person or group has placed on it. This is quite different, in my opinion, from saying that it is a prerequisite of a substantive legitimate expectation claim that the person relying on it must show that he or she has suffered a detriment.”
“64. The onus of establishing that a sufficiently clear and unambiguous promise or undertaking, sufficient to give rise to a legitimate expectation, is cast on the party claiming it …” Read more »