"It is clear that the mere fact that the judgment is by consent does not detract from its conclusive effect upon the issues determined by it: Re South American and Mexican Co; Ex parte Bank of England (1895) 1 Ch 37. But a judgment operates by way of estoppel only as to those matters which are necessarily decided by it. (Cf Blair v Curran [1939] HCA 23; (1939) 62 CLR 464, at 532; Jackson v Goldsmith (1950) 81 CLR, a 466). 'Though consent judgments and orders are undoubtedly in every case decisions in the sense that the actual mandatory or prohibitive parts of the judgment or order are conclusively binding upon ... the parties ... it may often be a matter of legitimate doubt and debate as to what, if any, particular questions or issues of right, title, or liability were, expressly or impliedly, the subject of the consent, and of the decision. For this purpose, as for all other purposes connected with the ascertainment of the subject-matter of a decision, the court will closely examine all such evidence, if any, as is available and admissible, and, by the aid of such materials, will ascertain whether any and what adjudication of matters in dispute was expressed, or necessarily involved, in the actual decision assented to.' (Spencer Bower on Res Judicata, 24, par 34.) Again, at 114, par 174, the learned author says: 'In the case of judgments and orders by consent ... it is absolutely essential to refer to the pleadings or affidavits of the parties, if the judgment or order is in a naked and general form, in order to ascertain what, if any, decision of particular questions or issues was impliedly consented or submitted to by the party against whom such consent ... judgment or order was made.'
To determine, therefore, what is necessarily decided by a judgment it is proper and essential to examine the record of the proceedings. (Robinson v Duleep Singh (1878) 11 Ch D 798; Houstoun v Marquis of Sligo (1885) 29 Ch D 448."