What is the current state of the law on parol evidence?

Both parties agree that the parol evidence rule was first delineated in Goss v. Nugent (1833), 5B Ad.58 (CA), where Denman C.J. made the following statement, at p. 64: “By the general rules of the common law, if there be a contract which has been reduced into writing, verbal evidence is not allowed to be given of what passed between the parties, either before the written instrument was made or during the time that it was in a state of preparation, so as to add to or subtract from or in any manner to vary or qualify the written agreement . . . .”