Argued that a general equitable principle applied here. He stated that "A promise intended to be binding, intended to be acted on, and in fact acted on, is binding insofar as its terms properly apply". He relied on the 'equitable waiver' case of Hughes v Metropolitan Railway (1877) A lease included a covenant which required the lessee to undertake repair if the lessor gave notice. The lessor (Hughes) gave notice and the lessee (railway company) responded by making an offer to sell their shares in the property under the lease back to the lessor. Negotiations continued and then broke down after some time. The lessor then claimed to be entitled to repossess the property on the basis that the lessee had failed to undertake the required repair within the time frame. >The lessee argued that there was an 'implied promise' that the repair did not have to be carried out if the negotiations were to be successful, and the period of notice would not start to count. } Per Lord Cairns ... it is the first principle on which all Courts of Equity proceed, that if parties have entered into definite and distinct terms involving certain legal results, certain penalties or legal forfeiture, afterwards by their own act or with their own consent enter upon a course of negotiation which has the effect of leading one of the parties to suppose that the strict rights arising under the contract will not be enforced, or will be kept in suspense, or held in abeyance, the person who otherwise might have enforced those rights will not be allowed to enforce them where it would be inequitable having regard to the dealings which have thus taken place between the parties. Does the doctrine of promissory estoppel completely destroy the doctrine of consideration? High Trees case had to do with part payment of debts, so, does it extinguish the rule/principle in Foakes v Beer? The doctrine of promissory estoppel is subject to certain requirements, and this leads to the suggestion that it is merely an exception/defence to the general doctrine of consideration and does not destroy it. To be able to enforce variations in a contract, there is need for agreement and provision of consideration. Part payment of a debt will not extinguish the debt, unless something that amounts to consideration is provided (as outlined in Pinnels' Case) or the other common law exceptions apply. Variation of a contract can be done without the provision of consideration under the doctrine of promissory estoppel. Supply of goods and services- a new promise which varies the contract when the promisee is only performing an existing obligation is binding on the promisor if the promisor receives a 'practical benefit' (Williams v Roffey Bros).
However, in relation to debts owed, and paying a different sum (which is in effect a variation of the original contract to pay a certain amount), what is position of the law ?.