In Stag Line v Foscolo Mango & Co. (1932) a clause in the bill of lading gave “liberty to call at any port in any order for bunkering or other purposes all as part of the contractual voyage”. The vessel had on board engineers to test newly installed machinery and deviated in order to drop off the engineers after their tests had been completed. Before the vessel regained her contractual route she was wrecked. The Court held that the deviation did not come within the clause. The words “other purposes” were to be construed as meaning calls at a port for some purpose having relation to the contract voyage and the engineers had been taken on board quite independently from any purposes connected with the contract voyage. Where there has been unjustifiable deviation the shipowner cannot rely on the exception clauses in the charter party and is then only entitled to rely on the exceptions available under common law such as Act of God, or loss by the Queen’s enemies if he can prove that the loss would have occurred even if no deviation had taken place. A shipowner cannot rely on any clause entitling him to limit his liability or to claim demurrage where there has been an unjustifiable deviation. In times of war, revolution or other similar disturbances the crew, vessel or cargo may be exposed to certain risks and in order to make sure the rights and obligations of the parties when the crew ship and cargo are exposed to such risks, it is usual to have a special war risk clause in the charter party. The charter party may contain a war cancellation clause or a war risk clause.