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Tool Metal Manufacturing v Tungsten [1955] 1 WLR 761 House of Lords

Tungsten had been infringing a patent right held by TMM. When TMM heard of this they waived all infringements in return for Tungsten paying 10% Royalty and also 30% 'compensation' if sales exceeded 50KG in any month. These sums were excessive but Tungsten agreed to pay them otherwise they would be faced with a claim for infringing the copyright. Tungsten struggled to make payments. They got into arrears during the war times and an agreement was reached to waive the 'compensation' payments during the war years.


TMM could not enforce the compensation payments during the war years but could enforce them on termination of the war. TMM were estopped from going back on their promise to waive the payments in equity. Generally promissory estoppel will merely suspend legal rights rather than extinguish them. However, where periodic payments are involved and a promise has been made to reduce the payments because of pressing circumstances which are not likely to persist, promissory estoppel can be used to extinguish legal rights.
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