“14. …….the ultimate aim of interpreting a provision in a contract, especially a commercial contract, is to determine what the parties meant by the language used, which involves ascertaining what a reasonable person would have understood the parties to have meant………….the relevant reasonable person is one who has all the background knowledge which would reasonably have been available to the parties in the situation in which they were at the time of the contract. ……… 21. The language used by the parties will often have more than one potential meaning. I would accept the submission made on behalf of the appellants that the exercise of construction is essentially one unitary exercise in which the court must consider the language used and ascertain what a reasonable person, that is a person who has all the background knowledge which would reasonably have been available to the parties in the situation in which they were at the time of the contract, would have understood the parties to have meant. In doing so, the court must have regard to all the relevant surrounding circumstances. If there are two possible constructions, the court is entitled to prefer the construction which is consistent with business common sense and to reject the other.”