“It is trite law that, if one party’s obligation to do something under a contract is contingent upon the happening of a particular event, the circumstances of that event must be identified unambiguously in the contract. It must be clear beyond doubt how and in what circumstances the relevant obligation has been triggered.”
“…. [the contract] established a machinery for Petroplus to be paid the invoiced amount notwithstanding that Shell contend that they are in breach of their contractual obligations. The machinery would be ineffective, and the contractual intention behind it frustrated, if Shell were permitted to withhold payment by challenging the calculation of the price by reference to the bill of lading quantity on the grounds of short delivery, or, as here, by challenging the calculation by reference to the bill of lading date on the grounds that it resulted from breach of contract on Petroplus' part.”