9 In Aon, the joint judgment held that given the requirements of similar provisions in the rules of court in the Australian Capital Territory, it is incumbent upon an applicant for amendment at trial "to tender an explanation as to why the matter was allowed to proceed to trial in its existing form"; there is no entitlement to amend a pleading subject to payment of costs by way of compensation; all matters relevant to the exercise of the discretion must be weighed; the fact of substantial delay and wasted costs (the concerns of case management) will assume importance on an application for leave to amend; statements which suggest only a limited application of case management principles in the High Court's earlier decision in Queensland v J L Holdings Pty Ltd [1997] HCA 1, (1997) 189 CLR 146 should no longer be applied; and limits will be placed upon parties' ability to effect pleading changes, particularly if litigation is advanced: at [105], [111], [112]. The joint judgment commented that there was no difference in the separate judgment of the Chief Justice as to the principles which should now be applied in relation to applications for amendment: at [116].
10 In the particular circumstances of this case. I think it is consistent with the statutory provisions and the principles discussed in Aon to grant the application for leave to amend. I accept the applicant's explanation that the amendment is responsive to an unanticipated statutory construction submission made by the second respondent on the second day of the hearing. The applicant responded with reasonable promptness, within days in written submissions, filed in accordance with a direction during the period in which the hearing had to be adjourned, foreshadowing a claim for the new injunctive relief in the event that the second respondent's submission were upheld. A multiplicity of proceedings should be avoided if that can be done without injustice to the second respondent; this would also avoid the risk of an Anshun estoppel if the injunction had to be claimed in subsequent proceedings. I cannot see that the amendment would cause any prejudice to the second respondent additional to that which would arise if the applicant were successful on the basis of the current claim. As to the second respondent's submission that the form of the state environmental policy might change by the time any such subsequent proceedings were brought, I do not think that I should look into that possibility. If the proposed amendment is allowed, the decision whether the new claim to relief should be granted will be on the basis of the law as it now stands.