Estoppel in English law
Estoppel by acquiescence

Woodhouse Israel Cocoa Ltd v Nigerian Produce Marketing Board held that a contract for the sale of some coffee beans was agreed to be payable in sterling. The sellers mistakenly sent an invoice stating price was payable in Nigerian pounds. At the time the value of sterling and the Nigerian pound was equal. The buyers accepted the delivery and invoice without objection. Subsequently, the value of sterling fell quite dramatically in relation to the Nigerian pound. The buyers then sought to revert to sterling as stated in the contract. The buyers conduct in accepting the invoice unquestionably amounted to an implied clear and unambiguous promise to accept on those terms.
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