Promissory estoppel is a legal doctrine that may be used to prevent a party from reneging on a promise or representation they have made. It is a principle of equity that can be invoked to prevent a party from relying on their strict legal rights where it would be unfair or unjust to do so. Although originally developed by the common law, it has been modified over time by equitable principles.
The doctrine was established in the case of Hughes v. Metropolitan Railway Co., in which Lord Cairns explained that if parties enter into a contract and subsequently enter into negotiations that lead one party to believe that the strict legal rights arising from the contract will not be enforced, the party that could have enforced those rights may be prevented from doing so. This principle may apply even when the promise or representation relates to future events or intentions.
The doctrine of promissory estoppel has been applied in various legal contexts, including contract law. In particular, it may be used to alter or modify an existing contract where one party has made a promise or representation that the other party has relied upon to their detriment. This can create an exception to the requirement for consideration in the making of a contract, which normally requires some form of exchange of value between the parties.
To invoke the doctrine of promissory estoppel in contract law, several requirements must be met. Firstly, there must be an existing contractual relationship between the parties. Secondly, the promise or representation made must amount to a clear indication that the party making it intended to affect the existing contract. Thirdly, the party raising the plea of estoppel must have relied on the promise or representation made by the other party. This reliance must have been to their detriment, meaning that they would suffer a loss if the promise was not honoured.
It is also sometimes argued that the party who is to benefit from the promise or representation must have acted equitably, meaning that they have not taken advantage of the other party. However, this is a matter of some debate and has not been conclusively settled by the courts.
Finally, it is unclear whether the operation of promissory estoppel completely abrogates the rights created under the original contract, or whether it merely suspends them for a period. This issue has not been fully resolved by the courts and may depend on the specific circumstances of each case.
In conclusion, promissory estoppel is an important legal doctrine that can be used to prevent a party from relying on their strict legal rights in certain circumstances. It may be applied in contract law to alter or modify an existing contract where a party has made a promise or representation that the other party has relied upon to their detriment. However, there are several requirements that must be met before the doctrine can be invoked, and the precise scope and operation of the doctrine remain the subject of ongoing debate and interpretation by the courts.