“The doctrine of legitimate expectation is not in the realm of estoppel. The court below thought it is a specie of estoppel. lt slipped. The cross-appellant is right to submit that the doctrine is not an estoppel. What the doctrine postulates is that where a public body or person acting in public authority has issued a promise or has been acting in a given way the members of the public who are to be affected by the scheme of conducting public affairs in the charted manner would, by law, require the promise or practice to be honoured or kept by the public body or person acting in public authority, save where there exists sound basis not to so insist on the settled scheme of conducting public affairs. The doctrine, therefore, enjoins public bodies to be fair, straight-forward and consistent in their dealings with the public. In other words, the doctrine of legitimate expectation is based on the existence of regular practice by a public body which the claimant can reasonably expect to continue or subsist and thus relies on the state of affairs to conduct or arrange his business or affairs in anticipation of the availability of the regular practice to cater for the case of the claimant. Fair and open dealing are the pillars of the doctrine. And fairness requires that the exercise of the doctrine of legitimate expectation be moored to full disclosure or utmost food faith by the potential beneficiary of the doctrine.”
– FBIR v. HALLIBURTON (WA) LTD (2014)