I shall not repeat the references I made in Lovell v. Lovell [1950] HCA 52; (1950) 81 C.L.R. 513, at pp. 532-534 to cases of the highest authority which appear to me to establish that the true principle limiting the manner in which appellate jurisdiction is exercised in respect of decisions involving discretionary judgment is that there is a strong presumption in favour of the correctness of the decision appealed from, and that that decision should therefore be affirmed unless the court of appeal is satisfied that it is clearly wrong. A degree of satisfaction sufficient to overcome the strength of the presumption may exist where there has been an error which consists in acting upon a wrong principle, or giving weight to extraneous or irrelevant matters, or failing to give weight or sufficient weight to relevant considerations, or making a mistake as to the facts. Again, the nature of the error may not be discoverable, but even so it is sufficient that the result is so unreasonable or plainly unjust that the appellate court may infer that there has been a failure properly to exercise the discretion which the law reposes in the court of first instance.