The second is Mr Evans' inability to say whether an applicant acting with diligence and vigour could, in the ordinary course of things, have reasonably been expected to overcome the problem by May 2002, having started in November 2001 (see paragraph 17 above).
30 The third message conveyed by the further evidence comes from Mr Gunnee, namely, that the application to vary the development consent conditions involves a significant degree of novelty. The effect of the application, if granted, will be to cause the relevant development consent condition to correspond with the requirements of Australian Standard AS 3959. Mr Gunnee was asked whether this would be the first occasion on which Hornsby Council had taken that course, assuming the application was successful. He replied that, in the nine years that he had been dealing with such matters, "probably the vast majority" had been cases in which "we" (which I take to mean the Rural Fire Authority) had requested or recommended something more than was required by AS 3959. The novelty of an application seeking requirements corresponding with those of AS 3959 may therefore be taken to be established. I have the distinct impression that it was this consideration that caused Mr Evans to be essentially non-committal when asked about the prospects of the success of the application for variation and the time it might take. There is also the point that Mr Willis was told by Mr Beck that the defendants might need to retain an expert on fire control regulations. This confirms that the matter was out of the ordinary.
31 The three new matters emerging from the further evidence - being, first, the established unreliability of what was originally accepted as the "blueprint" in Mr Fredericks' letter of 27 November 2002 (given its failure to recognise the now clear requirement for variation of the development consent conditions), second, the scope and possible timing of the process of obtaining such a variation (if granted at all) and, third, the significant novelty of an application to bring development consent conditions into line with AS 3959 - establish to my satisfaction that my original decision was founded on two fundamental misapprehensions as to the true factual position: first, that a building certificate could be obtained simply by following the steps in Mr Fredericks' letter of 27 November 2002 and, second, that the Council had effectively abandoned condition 25.18 of the development consent after the meeting of 9 April 2002. My previous findings on those two matters were central to my conclusion that the defendants were at fault when, after 9 April 2002, they did not pursue promptly and diligently the steps that, on the evidence then before me, would have resulted in the issue of the building certificate; and that that fault had such a causal relationship with non-availability of the building certificate that the defendants could not be permitted to rely on that non-availability.
32 The position as it is now shown to be is that if the defendants had acted promptly and diligently after 9 April 2002 to seek a building certificate, the Council, following the correct course outlined by Mr Evans rather than the incorrect course previously described by Mr Fredericks, would have stated that, notwithstanding Ms Van der Zanden's concurrence in the abandonment of the earlier variation application, it was necessary, in order to justify a s.88B covenant cast in terms of AS 3959 alone, to pursue to successful completion an application for variation of the development consent conditions. More fundamentally, the Council would not have issued the building certificate contemplated by the parties' contract unless the variation sought had been granted.
33 This reality, as it has now emerged, means that it cannot be regarded as at all certain that, even if the defendants had proceeded with reasonable promptness and diligence, the necessary building certificate would have been issued by the Council, whether within the period contemplated by the contract or at all. The application for variation of the development consent conditions would have been reviewed by the town planning department and by the Rural Fire Service. Ms Van der Zanden and Mr Gunnee may have played a role. It is also quite possible that other persons unfamiliar with what had happened in the past (except by referring to the files) would have become decision makers. The Rural Fire Service may still have raised a problem. The application would have been one attended by a significant degree of novelty. It might well have been seen as raising questions of precedent. The Council or a committee of the Council might have become involved in the decision making process. That process might have taken up to three months to complete and may never have produced an outcome favourable to the defendants.
34 All these factors of doubt and difficulty emerge clearly from the evidence led after re-opening. Because the issue of the building certificate is now seen to have been dependent on success of an application for variation of the consent conditions, all those factors undermine my previous conclusions. As the evidence now stands, I do not consider it possible to say that, had the defendants pursued matters with greater diligence after 9 April 2002 and completion of the physical work identified on that occasion, they could have reached in a relatively short time a point at which it was clear that all they needed to do to obtain the building certificate was to follow the steps that were later laid out for them in Mr Fredericks' letter of 27 November 2002. On the basis of the new evidence, they would never have reached such a point and would, even if acting with appropriate speed and diligence, have run up against the imponderables concerning variation of consent conditions that have now come to light.
35 In these circumstances, a finding of causal relationship between lack of activity and absence of the building certificate can no longer be justified, this being the essential determinant in a case of this kind: see The City of Gosford v Marim Pty Ltd (1990) 6 BPR 13,871. There are now shown to have existed substantial causal links in the chain beyond the reach of any diligence and effort the defendants could have brought to bear. In a case such as this, the party seeking to challenge rescission as inconsistent with the contract and wrongful faces a twofold task described as follows by Powell JA in Mitchell v Pattern Holdings Pty Ltd [2002] NSWCA 212:
"[I]t would have been incumbent on Mr. Mitchell to establish, first, that Pattern had failed to use all reasonable endeavours to procure the registration of a strata plan substantially in accordance with the draft strata plan, and, second, that it was Pattern's failure to use all reasonable endeavours so to do which led to the failure to have such a plan registered within 12 months of the date of the contract."