<Li> There are also exceptions to the parol evidence rule in construing a contract . The first exception is that there is evidence of trade usage, which is well - known, uniform and certain . Appleby v Pursell (1973) 2 NSWLR 879 . </Li> <P> Also, a narrow view of admissibility of extrinsic evidence has been taken, where evidence of surrounding circumstances is only admissible to resolve patent ambiguity, Cameron v Slutzkin (1923) 32CLR 81, latent ambiguity, Mainteck Services Pty v Stein Heurtey (2014) NSWCA 184 Lemming JA, and inherent ambiguity in the meaning of the words of a contract . The High Court in Electricity Generation Corporation v Woodside Energy Ltd took a different approach to interpreting commercial contracts, considering the "language used by the parties, the surrounding circumstances known to them and the commercial purpose or objects to be secured by the contract" at the "genesis of the transaction". This necessarily implies consideration of surrounding circumstances and indicates a broader approach may be adopted by the court in the future . The latest view is the narrow view which was described in Mount Bruce Mining Pty Limited v Wright Prospecting Pty Limited . </P> <Ul> <Li> See' LG Throne v Thomas Borthwick per Herron (dissent) which has been subsequently adopted . </Li> </Ul> <Li> See' LG Throne v Thomas Borthwick per Herron (dissent) which has been subsequently adopted . </Li>

When may oral evidence be introduced after a written contract has been agreed to