Discharge by frustration is where a party to a contract was prevented from keeping the promise because of an unforeseeable, intervening event, they are not liable for the breach (Taylor).
For frustration to be present, the court must decide whether performance is impossible in fact (Jackson).
A contract becoming illegal to perform after it is made frustrates the contract (Denny, Mott and Dickson Ltd).
The main purpose of the contract must be affected by the change, not just some aspect of it (Krell/ Herne Bay Steamboat Co.)
Self induced frustration is breach and frustration will not apply if the frustrating event is in control of one party (Maritime National Fish Ltd).
A contract becoming less profitable or more difficult to complete is not a reason for frustration (Davis Contractors).
If the event is a foreseeable risk and is mentioned in the contract, it cannot be frustration (Armchair Answercall).