Generally, an employer has the freedom to modify non-contractual terms at any time without securing the agreement of the employee, provided that this is not done in a discriminatory or inherently unreasonable manner. As to whether the employer can be estopped from doing so where it has promised, as in this case, that it will not withdraw an employee benefit scheme, will depend on the specific circumstances. Under the doctrine of promissory estoppel, where one party (the promisor) promises the other (the promisee) that they will not insist upon their strict rights under the contract, the promisor will not be allowed to resile from that position except upon giving reasonable notice. Further, if, by acting upon the promise, the promisee suffers prejudice, such as to make it inequitable for the promisor to go back on their promise, they will not be permitted to do so. In order successfully to invoke the doctrine, it is necessary