Here the Court of Appeal refined the earlier legal principle of Whitworth Street Estates v Miller (HL) that anything said or done after a contract was formed was inadmissible as evidence.
In Brian Royale Magg t/a BM Builders v Guy Marsh and others it held in cases of oral contracts that conduct evidence of the parties could be considered.
This was because the usual evidence would be oral witness testimony from the parties or other witnesses and it was accepted practice to test the recollections of such testimony to hear what the parties had said or done about the disputed matter in the meantime.
Accordingly conduct evidence subsequent to the formation of a contract- which would not be allowed in any dispute over the meaning of a written contract-would be allowed in an oral contract dispute but this would only be as a mechanism of testing the reliability of the parties’ recollections as to what the terms of the contract were.
Such conduct evidence accordingly would be given a very “short leash” and would still not be admissible directly as to what the terms of the contract were since conduct post formation of contract could be manipulated or distorted on purpose to seek to give an inaccurate impression of facts.
Courts are aware of instances of “play acting” by parties in order to seek to gain an unfair advantage and therefore tend to view such evidence with suspicion.
