The doctrine of frustration cannot override express and unambiguous contractual provision for the frustrating event. Commercial contracts often contain what is known as a force majeure clause, a clause that states what will happen to the contractual relationship between the parties should a particular sets of circumstances (which could otherwise amount to frustrating events) materialise. Force majeure clauses often refer to acts of terrorism, war and 'Acts of God'. The inclusion of a force majeure clause enables the parties to allocate risks in relation to these events at the outset and may allow for the continuance of the contractual relationship in circumstances that would otherwise amount to frustration of the contract.