“Where the sufferer from a breach of contract finds himself, in consequence of that breach placed in a position of embarrassment, the measures which he may be driven to adopt in order to extract himself ought not to be weighed in nice scales at the instance of the party whose breach of contract has occasioned a difficulty.  It is often easy after an emergency has passed to criticise the steps which have been taken to meet it, but such criticism does not come well from those who have themselves created the emergency. The law is satisfied if the party placed in a difficult position by reason of the breach of a duty owed to him has acted reasonably in the adoption of remedial measures and he will not be held disentitled to recover the cost of such measures merely because the party in breach can suggest that other measures less burdensome to him might have been taken.”

Banco de Portugal v Waterlow & Sons Ltd [1932] AC 452 at 456