The task of the court can be stated simply in the way in which Upjohn LJ stated it [in the Hong Kong Fir case]. First, see whether the stipulation, on its true construction, is a condition strictly so called, that is a stipulation such that, for any breach of it, the other party is entitled to treat himself as discharged. Second, if it is not such a condition, then look to the extent of the actual breach which has taken place. If it is such as to go to the root of the contract, the other party is entitled to treat himself as discharged; but otherwise not. To this may be added an anticipatory breach. If one party, before the day on which he is due to perform his part, shows by his words or conduct that he will not perform it in a vital respect when the day comes, the other party is entitled to treat himself as discharged.