"Those cases exhibit some degree of homogeneity, of course; but they also seem, at first sight, to exhibit a degree of semantic dichotomy. It is a discernible thread running through, I think, every one of those cases and the cases cited in them, that it is not decisive of an appeal in this court from the decision of the court below, exercising the particular discretionary jurisdiction of deciding the custody of children (but also, I think, any discretionary jurisdiction), that the result of the exercise of discretion would, or might, have been different if the members of the Court of Appeal had themselves been exercising the discretion. There has to be more than that before the discretionary decision can be overturned. The question, if there be one, is: How much more?"
"I believe that there is a way of reconciling these cases. I believe that if the court comes to the conclusion, when examining the decision at first instance, that there is so blatant an error in the conclusion that it could only have been reached if the judge below had erred in his method of decision - sometimes called the balancing exercise - then the court is at liberty to interfere; but that, if the observation of the appellate court extends no further than that the decision in terms of the result of the balancing exercise was one with which, they might, or do, disagree as a matter of result, then that by itself is not enough, and that falls short of the conclusion, which is essential, that the judge has erred in his method. I cannot think of any case in which this particular issue has had to be faced, in which that method of determination is not intellectually satisfactory, logically supportable or consistent with the result of any of the cases in the appellate courts; and I shall approach this case on the footing that what this court should seek to do is to answer the question whether the court discerns a wrongness in the result of so striking a character as to make it a legitimate conclusion that there must have been an error of method - apart, of course, from a disclosed inclusion of irrelevant or exclusion of relevant matters."
"There was not really a right solution; there were two alternative wrong solutions. The problem of the judge was to appreciate the factors pointing in each direction and to decide which of the two bad solutions was the least dangerous, having regard to the long-term interests of the children, and so he decided the latter. Whether I would have decided it the same way if I had been in the position -of the trial judge I do not know. I might have taken the same course as the judge and I might not, but I was never in that situation. I am sitting in the Court of Appeal deciding a quite different question: has it been shown that the judge to whom Parliament has confided the exercise of discretion, plainly got the wrong answer? I emphasise the word 'plainly.' In spite of the efforts of [counsel] the answer to that question clearly must be that the judge has not been shown plainly to have got it wrong."
"It is, of course, not enough for the wife to establish that this court might, or would, have made a different order. We are here concerned with a judicial discretion, and it is of the essence of such a discretion that on the same evidence two different minds might reach widely different decisions without either being appealable. It is only where the decision exceeds the generous ambit within which reasonable disagreement is possible, and is, in fact, plainly wrong, that an appellate body is entitled to interfere."
"But at the end of the day the court may not intervene unless it is satisfied either that the judge exercised his discretion upon a wrong principle or that, the judge's decision being so plainly wrong, he must have exercised his discretion wrongly."
"Apart from the effect of seeing and hearing witnesses, I cannot see why the general principle applicable to the exercise of the discretion in respect of infants should be any different from the general principle applicable to any other form of discretion."
"Can this conclusion prevail or is there some rule of law which bars it? The judge was exercising a discretion. He saw and heard the witnesses. It is impossible to say that he considered any irrelevant matter, left out of account any relevant matter, erred in law, or applied any wrong principle. On the view I take, his error was in the balancing exercise. He either gave too little weight to the factors favourable, or too much weight to the factors adverse to the father's claim that he should retain care and control of the child.
"The general principle is clear. If this were a discretion not depending on the judge having seen and heard the witnesses, an error in the balancing exercise, if I may adopt that phrase for short, would entitle the appellate court to reverse his decision [authorities cited]. The reason for a practical limitation on the scope of that principle where the discretion exercised depends on seeing and hearing witnesses is obvious. The appellate court cannot interfere if it lacks the essential material on which the balancing exercise depended. But the importance of seeing and hearing witnesses may vary very greatly according to the circumstances of individual cases. If in any discretion case concerning children the appellate court can clearly detect that a conclusion, which is neither dependent on nor justified by the trial judge's advantage in seeing and hearing witnesses, is vitiated by an error in the balancing exercise, I should be very reluctant to hold that it is powerless to interfere."
"It should be borne in mind that the members of the Appellate Committee will have also read the judgments in the courts below. The case should, accordingly, start with a statement of what the party conceives to be the issues that arise on the appeal. In an appeal to this House, these are generally questions of law or (as in the instant case) of the exercise of a judicial discretion, although occasionally a party may want to challenge a finding of fact. . . . The case should set out the heads, but no more than the heads, of the argument upon each of the issues which it is intended should be advanced by counsel for the party at the oral hearing to challenge or support, as the case may be, the decision on that issue of the court from which the appeal is brought. Detailed or elaborate argument adds unnecessarily to the costs of preparing the case and is seldom helpful or time-saving at the oral hearing. Reference to authorities relied upon in support of the argument on any issue should be limited to key authorities (seldom numbering more than one or two on any one issue) which lay down the principle which it is contended is applicable, and the particular passage or passages in the judgments in which the principle is stated should be identified and, unless unduly lengthy, may helpfully be quoted verbatim. But references to numerous other cases in which that principle has been previously applied by courts to particular facts which it is claimed may be regarded as presenting some analogies to the facts of the case under appeal are usually out of place in the written case and, I may add, more often than not turn out to be time-wasting in oral argument also. . . ."
"The law as to the reversal by a court of appeal of an order made by the judge below in the exercise of his discretion is well-established, and any difficulty that arises is due only to the application of well-settled principles in an individual case. The appellate tribunal is not at liberty merely to substitute its own exercise of discretion for the discretion already exercised by the judge. In other words, appellate authorities ought not to reverse the order merely because they would themselves have exercised the original discretion, had it attached to them, in a different way. But if the appellate tribunal reaches the clear conclusion that there has been a wrongful exercise of discretion in that no weight, or no sufficient weight, has been given to relevant considerations such as those urged before us by the appellant, then the reversal of the order on appeal may be justified."