28 Spigelman CJ said (at [16]) (emphasis added):-
It must be the case, and indeed was common ground, that there be some restriction on the ability of the Trust to determine a rent payable pursuant to the lease. That restriction is either found in the terms of a criterion such as a 'fair and reasonable' rent, or it is found in the specification of the facts and matters to which the Trust "may have regard" under cl 4(b)(iv). If the latter is exhaustive, then there is neither room, nor need, for an implied term .
29 That passage is important for two reasons: first, that although His Honour said (at [12]), in the passage relied upon by Mr Newlinds, that it was no objection to enforceability of a contract that it left to a party determination of a price or payment, such a power to determine the price or payment would be restricted either by criteria expressly provided by the contract, or by an implied term such as that it be fair and reasonable; and secondly, that if the contract provided the requisite criteria, there was not then room to imply a term that the rent be "fair and reasonable".
30 In Kabwand Pty Limited v National Australia Bank Ltd (1989) ATPR 40-950, the Full Court of the Federal Court considered a clause in a loan agreement which provided for the payment of interest at 15.25 percent subject to the Bank, at its discretion, varying that rate "conforming with general movements in the Bank's interest rates". The borrower argued that that provision was void for uncertainty. The Court (Lockhart, Hartigan and Hill JJ) identified that there were, in fact, three relevant principles. The first is that if parties to a contract do not agree on a fundamental term there will be no contract at all [G Scammell & Nephew Limited v HC & JC Ouston [1941] AC 251; Kabwand]. The second is that there is no contract if its effect is that one party is left to choose whether or not it will perform it, since the obligation is illusory [Thorby v Goldberg (1964) 112 CLR 597; Godecke v Kirwan; Kabwand). The third is that there can be no concluded bargain if a vital matter has been left to the determination of one of the parties [Placer v The Commonwealth; Godecke v Kirwan; Kabwand]. In Kabwand, as in the present case, it was the third of those principles which was of potential application. The Court concluded in these terms:
Whatever may be the case where a loan agreement provides that the lender may select any interest rate it pleases, the present is not that case. Here the rate of increase or decrease of interest must conform to the general rates of interest charged to customers of the bank, that is to say there is an objective market standard to be applied at all times. In these circumstances we do not think that it can be said that any of the three principles sought to be applied have application. As the trial Judge said, and we agree, the present clauses as to interest are "not to be construed as giving to the cross claimant a power at large. A borrower may challenge any increase on the basis that it has been fixed otherwise than in conformity with the general movements referred to".
31 In Cross v National Australia Bank Limited (FCA, 29 April 1994, unreported) Drummond J held a provision in a lease, which empowered the lessor (which was a bank) to recover interest from the lessee on any arrears of rental and on the accelerated future rentals from the due dates until payment "at such rate as is determined by the bank from time to time" - it not being suggested that this could be read as a reference even to the bank's own benchmark rate - was void and illusory, but severable.
32 These cases establish that while determination of a price or payment under a contract may be left to the party entitled to receive the price or payment, that will be so only where there are criteria - either express, or such implied criteria as "fair and reasonable" - by which that party's decision can be tested, and that where an express formula is provided, there is no room to imply criteria such as "fair and reasonable". In Royal Botanic Gardens and in Kabwand, there were such criteria; in Cross there were not.
33 If the provision relating to interest be void in the present case, it must be because the mechanism for its calculation infringes the third principle, since this is not a case in which the parties have not agreed on a fundamental term, nor is it a case in which one party has been left to choose whether it will perform the contract. The question is whether a vital matter, namely the rate of interest - or more precisely, one component of it, being the benchmark rate - has been left to the determination of one of the parties, namely Perpetual, without a criteria against which Perpetual's determination can be tested. That makes it necessary to construe the definition of "Benchmark Rate" in clause 1.1, particularly having regard to its second sentence, which provides that in determining the benchmark rate the lender will, without having any obligation to do so, refer to the 90 day bank bill rate. There would be considerable force in the argument that the Benchmark rate was to be the 90-day bill rate, were it not for the direct inconsistency between the apparent obligation imposed on Perpetual to refer to the 90 day bill rate, and the express statement that it has no obligation to do so. The two simply cannot sit together and to my mind there is no sensible reconciliation of them which does not involve doing violence to the language of the clause. I do not think it is possible to disregard the words "but without having any obligation to do so", which have presumably been deliberately included in the definition. Either the second sentence in the definition is incapable of being given sensible meaning, or the proviso that there is no obligation to have regard to the 90-day rate prevails over the initial statement that the lender will have regard to that rate.
34 I do not accept the submission that I should resort to pre-contractual letters of offer to construe the contract. While the letter of offer states that the interest rate was to be the 90-day bill rate plus 3%, that is not what the contract provided. In my opinion it would be impermissible to use that letter of offer as illustrating the intentions of the parties [Codelfa Construction Pty Ltd v State Rail Authority of New South Wales (1982) 194 CLR 337, 352 (Mason J).
35 Accordingly, in my opinion, clause 1.1 of the Term Loan Agreement must be read as leaving the Benchmark Rate to be determined by the lender without any constraint or reference criteria, and that distinguishes the case from Kabwand and brings it within the judgment of Drummond J in Cross. For that reason, I think the provision which confers on the lender the ability to determine whatever Benchmark Rate it likes is void. I do not accept Mr Newlinds' argument that, if the provision relating to determination of the Benchmark Rate is void, the Court can substitute a "fair and reasonable" rate: consistently with Royal Botanic Gardens, there is no room to imply such a term where the parties have made provision for a particular formula and criteria.