The 'Parol Evidence' Rule
Invalidation by misrep or mistake
If a claimant finds out something in the contract is false then he can introduce evidence
The 'parol evidence' rule means that
If a contract is in writing, then any spoken or other evidence that contradicts or adds to the written agreement would be dismissed
If written agreement only represents part of a larger agreement
J Evans & Son v Andrea Merzario (1976)
When the contract relies on fulfillment of an event
Pym v Campbell (1856)
Custom or trade usage
Term can be implied into a contract by trade or custom
Rectification - where it can be shown that the written agreement did not reflect the actual agreement
Webster v Cecil (1861)
Collateral contracts
Westminster Properties v Mudd (1958)