"When by the nature of the contract its performance depends on the existence of a particular thing or state of things, the failure or destruction of that thing or state of things, without default on either side, liberates both parties"
"After the formation of a contract, certain sets of circumstances arise which, owing to the fault of neither party, render fulfilment of the contract by one or both of the parties impossible in any sense or mode contemplated by them. These sets of circumstances have been more or less defined by the Courts and are held by them to release both parties from any further obligation to fulfil the contract."
"Whereas it has been arranged between the parties that the First Parties [the respondents] shall
"In the event of the foregoing trading agreement being terminated by either party as aforesaid"
"and may be terminated at the instance of the Second Parties by their giving at least twelve calendar months' notice in writing by registered letter prior to the date on which the termination shall take place, and the First Parties shall have the right to terminate the agreement at their instance on giving three years' notice of termination in writing by registered letter of the date on which the termination is to take place."
"Further, it is to be observed that the disturbing cause must go to the extent of substantially preventing the performance of the whole contract. Interference leaving a considerable part capable of performance will not be an excuse."