判决理由
Promissory estoppel can only be used as a defence (a shield), not as a cause of action (a sword). It does not create new rights but prevents a party from going back on a promise in certain circumstances.
事实
After divorce, the husband promised to pay his ex-wife £100 per year maintenance. He never paid. She did not apply to the court for maintenance, relying on his promise. She then sued on the promise. At first instance, she succeeded on the basis of promissory estoppel.
判决摘要
The Court of Appeal reversed the decision. Denning LJ held that promissory estoppel, as described in High Trees, could not be used as a cause of action. It was a principle of equity designed to prevent injustice, not to create new causes of action where none existed. The wife's claim failed for want of consideration.
关键引述
"The principle does not create new causes of action where none existed before. It only prevents a party from insisting upon his strict legal rights, when it would be unjust to allow him to enforce them."
— Denning LJ
后续处理
Definitive authority that promissory estoppel operates as a shield, not a sword. Consistently followed.