Despite what might otherwise have been inferred from this submission, it was apparently not intended to be an attack on the credibility of Mr Bailey's evidence that the advice received did not cause him to expect the wall to collapse. The point made was rather that Mr Bailey's conduct, based on his belief, did not meet an objective criterion of reasonableness as between the plaintiffs on the one hand and the Engineer and the Architect on the other. That is, whatever Mr Bailey's belief, "an objectively reasonable person" would have concluded from the 9 July 1992 report in particular that the wall was at risk of being blown over.
72 The Engineer and the Architect made two concluding submissions. One was put thus. It was said that Mr Bailey's evidence that Mr Aplin's report was simply the report of one engineer about another's work:
"does not ring true. Mr Bailey had no reason to doubt the accuracy of the advice that he received from Mr Aplin. He did not question the adequacy of the rectification works proposed by Mr Aplin. In July 1992, Mr Aplin informed Mr Bailey that the work done by the Engineer on the first stage was 'not up to standard'. Mr Bailey believed that the work was 'not up to standard' and he would not have believed the Engineer as to whether he said the work was good or not. By November 1992, Mr Bailey had discussed with Mr Aplin the need to 'completely re-do' the Engineer's work. He could afford to undertake the remedial work which he was advised would remedy the defects. He had a period of in excess of two years in which to effect the recommended remedial works."
73 The other concluding submission attacked the trial judge's conclusion that there was "no demonstrated prospect" that Mr Aplin's repairs would have averted the damage that occurred in 1994. The submission was:
"With respect, there is no factual foundation for this conclusion. At the time of being confronted with this decision (in or about July 1992) the plaintiffs did not know that there was no demonstrated prospect that damage to the building would not be averted if they carried out remedial work. On the contrary, they had a capable and responsible engineer in the form of Mr Aplin advising them that the rectification works would make the wall sound. The fact that subsequent expert opinion proffered in the course of litigation offered a different view (that was accepted by the trial Judge) cannot affect what was reasonable or not for Mr Bailey to do in July 1992 confronted with credible advice as to how to solve the problem."
74 It is convenient to deal with this last submission first. If, as the Engineer and the Architect contended at some points, the relevant test is purely objective, it cannot be unreasonable to fail to undertake steps which, in the light of all the evidence, would not have averted the damage. The present submission depends on criticising the plaintiffs for not acting on advice from Mr Aplin (who deliberately concealed his perception of the true extent of the peril from them) which in fact would have been useless. But since it is not essential that the finding under attack be called in aid to support the trial judge's conclusion that the plaintiffs behaved reasonably, it need not be dealt with further.
75 So far as the penultimate submission is concerned, it consists of an attack on evidence of Mr Bailey on which the trial judge did not explicitly rely, though he did refer to it with apparent favour (Red 78N-P). Even if the trial judge relied on it, it is not essential to support his reasoning. In any event, there is no finding at all by the trial judge critical of Mr Bailey's credibility in any respect, and no convincing reason is assigned by the Engineer and the Architect as to why the evidence in question should be rejected. Hence, if the trial judge did take account of the evidence in arriving at his conclusions, it was not erroneous of him to have done so.
76 The other submissions of the Engineer and the Architect do not indicate that the trial judge's conclusion on reasonableness was wrong. It is supportable for numerous reasons, not all of which were advanced by the trial judge.
77 A plaintiff "cannot be said to have really incurred any loss which might have been avoided by his taking such steps as a reasonably prudent man in his position would have taken to avoid further loss to himself": Driver v War Services Homes Commissioner (1923) 44 ALT 130 at 134 per Irvine CJ (emphasis added). A plaintiff cannot recover damages for losses "which he would not have incurred had he acted reasonably in the ordinary course of his business": TCN Channel 9 Pty Ltd v Hayden Enterprises Pty Ltd (1989) 16 NSWLR 130 at 162 per Priestley JA (emphasis added). Subject to the criterion of reasonableness, the plaintiff "is completely free to act as he judges to be in his best interests": The Soholt [1983] 1 Lloyd's Rep 605 at 608 per Sir John Donaldson MR (emphasis added). "The word 'reasonable' has in law the prima facie meaning of reasonable in regard to those existing circumstances of which the actor, called on to act reasonably, knows or ought to know": In re a Solicitor [1945] KB 368 at 371 per Scott, Lawrence and Morton LJJ; see also Adams v Eta Foods Ltd (1987) 78 ALR 611 at 621 per Gummow J.
78 Hence the question is what was reasonable for persons in the position of the plaintiffs, and in particular for a person in the position of Mr Bailey, consulting his own interests in relation to his own building project. Mr Bailey was not a structural engineer. By 9 July 1992, the Engineer and the Architect had completed all their duties in relation to stage one, and had been paid. The plaintiffs owed the Engineer and the Architect no duties and had no continuing relationship in connection with stage one. Short of suing them, he had no power over them. All the reports from 9 July 1992 on (like that of 9 May 1992) were obtained for the purposes of litigation against the builder (Blue 1/163T; 79N; 81M; and 96S). All of the reports were supplied for that purpose (the 4 December 1992 report was headed "Additional Comments to Scott Schedule" (Blue 1/98)). All the reports were brief. Thus all were angled towards recovery of monies in litigation against the builder; none were angled towards the issue of whether extensive damage might be caused by the problems identified, and how much. None of them suggested that there was any urgency in carrying out the steps recommended in relation to a building which human beings would from time to time enter. In short, they described what steps should be carried out, and what those steps would cost, not because any person was suggesting that an acute practical problem had to be met urgently, but in order to permit the quantification of the second defendant's cross claim against the builder. Though the Engineer and the Architect contended that Mr Bailey ought to have inferred from the 9 July 1992 report that Mr Aplin thought the wall would collapse, his failure to do so is excusable in view of Mr Aplin's deliberate non-disclosure of that probability and deliberate decision to use language not suggesting it. There is no evidence that either Mr Bailey's solicitor or Mr Maber, to whom the 9 July 1992 report was sent (Blue 1/79), read it as indicating a possibility of collapse. Thus Mr Bailey's belief that the wall would not collapse may have been wrong, but it was not unreasonable. Mr Bailey was not told anything about what chance there was that wind might damage the building, and to what extent, beyond the general remarks in the 9 July 1992 report about the wall being "inadequate for the wind loads" and about a "possibility" that the "top courses of brick work may be dislodged".
79 It was open to a reasonable man in the position of Mr Bailey to take the view (though this view did not entirely correspond with Mr Bailey's actual view (Black 78B-79J)) that if he spent the $7,800 in carrying out (inter alia) Mr Aplin's recommendations, he would not be able to recover that sum from the builder if it stemmed from a deficiency on the part of the Engineer or the Architect; that he certainly would not be able to recover it from the builder after the second defendant settled its proceedings against the builder on 6 April 1992 on terms that the former pay the latter $3,750 (Blue 1/101); and that instituting fresh proceedings against the Engineer or the Architect to recover the $7,800 would be an imprudent and not very useful step. Mr Bailey, though appreciating that the advice to him was that the wall was unstable (Black 42N-P and 46U-W), did not think that "the wall may not be safe" (Black 42L-M) or was in danger of falling down (Black 45N-R) but only thought that cracking in the wall was a possibility (Black 42R-T) arising from the instability. It was open to a reasonable man in the position of Mr Bailey to assume that if he kept an eye on the units to observe the progress of any cracking (Black 42X-43E and 46J-P), the remedial work and any argument with the Engineer could be postponed until the severity of the problem became clear; and since no cracks did appear in the two years or so before the storm (Black 43N-S, 57N-P and 72M-S), the wall did not require remedial work. A reasonable man in Mr Bailey's position might also take into account the fact that an estimate of $7,800 for the cost of building work might well turn out to be less than what actually would have to be spent, in the light of common experience of the tendency of building costs to rise rather than to fall. While Mr Bailey may well have been able to find $7,800 or even some larger sum, he was under sufficient financial pressure to cause him to postpone stage two of the project. It was open to a reasonable man in Mr Bailey's position to take the view that once his plans to build the other four units proceeded, any deficiency in the existing units could be repaired without having to pay out $7,800 immediately in circumstances which would make it difficult to recoup the money from any other person. While a reasonable man in Mr Bailey's position might well be held to have behaved unreasonably if he failed to spend $7,800 or some higher sum on repairs if he thought a collapse was probable or possible, the conclusion may legitimately be quite different if the only perceived risk was instability producing cracking.
80 The Engineer and the Architect conceded that at least so far as mitigation and contributory negligence were concerned, they bore the burden of proving unreasonableness, and appeared to make the same concession in relation to causation so far as novus actus interveniens doctrines were concerned. Wherever the burden of proof lay in relation to aggravation, once the trial judge made findings that the plaintiffs had not behaved unreasonably, the Engineer and the Architect on appeal had to demonstrate not merely that some other judge might have come to a different conclusion, but that the view to which this trial judge came was appellably wrong. While the trial judge's decision as to reasonableness was not discretionary in character, it was a decision turning on matters of judgment and degree, and on an evaluation of competing considerations; it was lengthy and detailed; it was the product of an apparently careful approach; and it depended on analysing Mr Bailey's actual and possible attitudes on a question in relation to which he was the best judge and in relation to which, subject to the overriding criterion of reasonableness, he had considerable freedom of judgment, namely the question of where his best interests lay. It is not easy to overturn on appeal a judgment having those characteristics. In my opinion the present attempt to do so does not succeed for the reasons just set out.
81 The Engineer and the Architect accepted that if their challenge to the trial judge's findings about reasonableness did not succeed, then it was not possible to reduce the damages awarded by the trial judge. This makes it unnecessary to decide several controversies about whether the plaintiffs could be said to have aggravated damage, about where the burden of proof lay if that could be said, and about the relationship between aggravating damage and not mitigating damage. It is also not necessary to decide whether the Engineer and the Architect successfully made out a challenge to the trial judge's conclusion that even if Mr Aplin's recommendations had been carried out, the collapse would probably have occurred. Nor is it necessary to consider submissions based on a passage in the reasons for judgment of Burt J (delivered on behalf of the Full Court consisting of himself, Jackson CJ and Lavan J) in Plenty v Argus [1975] WAR 155 at 158 dealing with the relevance of the prospects of success in medical treatment of the plaintiff's injury to the question of whether the plaintiff reasonably refused treatment; compare 159, where the discounting of damages once unreasonableness has been found is discussed. The case was referred to below by both Engineer and Architect. However, it was said below by the Engineer not to be relevant where the plaintiffs had aggravated damages, as according to the Engineer they had (Engineer's written submissions dated 9 July 1999, paragraph 2.10 (4)). Indeed the oral address went further in saying that Plenty v Argus had no application to the present case "in any way shape or form" and that it had "no work to do in this case" (Black 211W-212X). On appeal the Engineer took the opposite tack, submitting, after quoting page 158, that the plaintiffs' "conduct was an aggravation of the pre-existing damages and that damages should be reduced to reflect the chance that if Mr Bailey had acted reasonably the damage would have been averted in whole or in part" (Engineer's written submissions dated 13 September 2000, paragraph 34). The Architect both below and on appeal relied on the case as part of its argument on aggravation of damages. The differences between the positions of the Architect and the Engineer at trial, and between the Engineer's position at trial and the Engineer's position on appeal, do not create a promising background for the submission made orally that the trial judge's treatment of Plenty v Argus (Red 87D-T and 90V-X) was "confused" (transcript page 7 line 52). In any event, even if the remedial treatment would probably have succeeded, or enjoyed a chance of success which though it was less than probability, was significant or more than trivial, it has not been demonstrated that it was unreasonable in all the circumstances in which the plaintiffs found themselves for them not to spend the money on remedial treatment. Plenty v Argus is thus not determinative of the present case and its significance, if any, in some other case need not be explored here.