HI-TECH INVESTMENT LIMITED V WORLD AVIATION SYSTEMS (AUSTRALIA) PTY LIMITED HC AK CIV 2008-404-004189

HI-TECH INVESTMENT LIMITED V WORLD AVIATION SYSTEMS (AUSTRALIA) PTY LIMITED HC AK CIV 2008-404-004189 16 December 2008IN THE HIGH COURT OF NEW ZEALAND AUCKLAND REGISTRY CIV 2008-404-004189UNDER ARBITRATION ACT 1996 BETWEEN HI-TECH INVESTMENT LIMITED Appellant AND WORLD AVIATION SYSTEMS (AUSTRALIA) PTY LIMITED Respondent Hearing: 27 November 2008 Appearances: D F Dugdale and K Davis for Appellant WMJ Marsh for Respondent Judgment: 16 December 2008RESERVED JUDGMENT OF PRIESTLEY JThis judgment was delivered by me on 16 December 2008 at 11.45 a.m. pursuant to Rule 540(4) of the High Court Rules. Registrar/Deputy Registrar Date: Counsel/Solicitors: D F Dugdale, P O Box 46-281, Herne Bay, Auckland 1001. Fax: 09 368 5613 K Davis, P O Box 26-717, Epsom, Auckland 1005. Fax: 09 522 2758 WMJ Marsh, P O Box 128 535, Auckland 1541. Fax: 09 524 0205 PWG Ahem, Morrison Kent, P O Box 222, Shortland Street, Auckland 1140. Fax: 09 309 3797Introduction[1] The appellant and respondent were landlord and tenant respectively of commercial premises at 396 Queen Street, Auckland. [2] Three separate leases were involved. The first Deed of Lease concluded on 21 January 2003 covered Level 13 of the building and five linked carparks. The second Deed of Lease was concluded in March 2004 and covered part of Level 9 plus two carparks. A third lease relating to a smaller area of Level 9, was concluded in January 2005. [3] All Deeds of Lease were completed on the then current Auckland District Law Society (3rd ed 1993) form, to which various alterations have been made. [4] The appellant was not an original party to two of the Deeds of Lease. It purchased their reversion from the original lessor, Levonia Holdings Limited (Levonia), in March 2004. The lease for the 13th floor stipulated a 6-year term, commencing 1 October 2002. The agreed annual rental (exclusive of the five carparks) was $79,921.62 plus GST. [5] The lease provided for a rental review. It also contained mechanisms for the review and for disputes arising out of it. The rent review date was 1 October 2005, midway through the 6 year term. The same rent review date was contained in the other two Deeds of Lease. [6] The rent being paid, however, for the 13th floor during the first three years of the term was not the stipulated rent but the lesser annual figure of $50,493.29. This was because a rental discount had been agreed between the respondent and Levonia. This discount was the subject of a side-agreement evidenced in a letter dated 28 January 2003 from the then landlord's property managers to the respondent. Described as "a rent-free holiday", the total concession was in excess of $88,000 plus GST, spread over the first three years of the lease.[7] On 1 April 2004 the appellant, having completed due diligence, became the owner of the building and took over its management from Levonia and its agents. On becoming the owner it took over the reversion of the first two leases. In June 2005 a further lease by way of addendum was entered into relating to the smaller area on Level 9. [8] Over the next eighteen months the respondent noticed and, indeed, complained about a marked deterioration in building management and maintenance. That deterioration subsequently led the respondent to claim that the level of its enjoyment of the leased premises was progressively diminishing. [9] As the rent review date approached, a Mr Choi, who was the appellant's property manager, researched the position. He prepared a notice pursuant to the terms of the lease, which was served on the respondent as tenant on 27 September 2005. [10] So far as the rent for Level 13 was concerned, the notice (using GST exclusive figures) increased the annual rental for Level 13 from $50,493.29 to $53,946.62 and the rent for the five existing carparks from $15,600 to $16,661.91. [11] The 27 September notice prepared by Mr Choi enclosed tax invoices for the revised rental figures and sought new monthly bank automatic payments. The respondent made the first monthly payment of the reviewed rent on 1 October 2005. [12] Unfortunately for the appellant Mr Choi had made an error. Instead of calculating the rent review on the basis of the sum stipulated in the 21 January 2003 Deed of Lease, he instead based his calculations on the concessional $50,493.29 figure. [13] Some weeks would pass before the appellant became aware of Mr Choi's error. On 11 November 2005 the appellant issued a second notice purporting to review the rent on the basis of the higher $79,921.62 figure. The second notice, however, failed to correct the flow-on effect of the 27 September error on Level 9 rents.[14] It is unnecessary for me to stipulate the interrelationship between the January 2003 lease and the March 2004 lease relating to Level 9. The parties agree on the consequences. This omission so far as Level 9 was concerned was the subject of a third notice claiming a further adjustment sent to the respondent on 19 March 2006. [15] From this narrative it will be abundantly clear that the issue dividing the parties is whether the appellant is stuck with the figures contained in the 27 September 2005 notice for the second three years of the lease term, or whether the law permits the appellant to salvage its error.The lease[16] The lease dated 21 January 2003 between Levonia and the respondent relevantly provides in its Second Schedule:Rent Review2.1 THE annual rent may be reviewed by the Landlord as follows: (a) The Landlord shall commence a review by not earlier than three (3) months prior to a review date or at any time up to the next following review date giving written notice to the Tenant specifying the annual rent considered by the Landlord to be the current market rent as at that review date. (b) If, by written notice to the Landlord within twenty-eight (28) days after receipt of the Landlord's notice, the Tenant disputes that the proposed new annual rent is the current market rent then the new rent shall be determined in accordance with clause 2.2. BUT the new rent shall not be less than the annual rent payable during the period of twelve (12) months immediately preceding the relevant review date. (c) If the Tenant fails to give such notice (time being of the essence) the Tenant shall be deemed to have accepted the annual rent specified in the Landlord's notice. (d) The annual rent so determined or accepted shall be the annual rent from the review date or the date of the Landlord's notice if such notice is given later than three (3) months after the review date. (e) Pending the determination of the new rent, the Tenant shall pay the rent specified in the Landlord's notice provided that the rent is substantiated by a registered valuer's report.Upon determination of the new rent an appropriate adjustment shall be made. (f) The rent review at the option of either party may be recorded in a Deed, the cost of which and the stamp duty thereon shall be payable by the Tenant.[17] The next clause (it being, in my judgment, of some relevance that it had been left in the lease), is cl 2.2 which provides a mechanism if the parties are unable to agree on the current market rent within 14 days of the tenant's receipt of the landlord's notice. The terms are standard and unremarkable. One party can give the other a notice of arbitration. Alternatively, the parties may appoint valuers to either agree on the current market rent or submit it for determination by an umpire. [18] The fourth schedule of the lease contains a further rent review provision, cl 2.2.1, which specifically modifies the ratchet provision in cl 2.1(b) (supra [16]). Cl 2.2.1 provides:Clause 2.1(b): Delete the words "BUT the new rent shall not be less than the annual rent payable during the period of twelve (12) months immediately preceding the relevant review date" and insert the following words in their place "BUT the new rent shall not be less than the rent payable at the Commencement Date of this Lease and the new rent shall not be greater than the annual rent payable during the period of twelve (12) months immediately preceding the relevant review date as increased by the same percentage as the cumulative percentage increase in the Consumers Price Index (All Groups) as last published by Statistics New Zealand immediately before the commencement date or the immediately preceding review date (whichever is the later) and the relevant review date".The bolded emphasis appears in the lease. [19] Thus, salient features of these lease terms, it being almost trite to observe that they form part of a commercial document binding commercial parties, are:• If the tenant gives the landlord written notice within 28 days of receipt of the landlord's notice that the proposed new annual rent is disputed, then cl 2.2 governs the determination of the new rent (the unmodified portion of cl 2.1(b)).• If the tenant, time being of the essence, fails to give such notice within 28 days, then it is deemed to have accepted the annual rent specified in the landlord's notice (cl 2.1(c)).• If the tenant disputes the landlord's new proposed rent, then the new rent shall not be less than the rent payable at the commencement date of the lease and not greater than the rent payable during the preceding twelve months plus the same percentage of the published CPI increase (cl 2.2.1). [20] Obvious issues arising out of the clauses are: a) By taking no steps in the 28 days following its receipt of the 27 September 2005 notice from the landlord, can the respondent claim that it has accepted the annual rent specified in Mr Choi's notice, with the result that there is a concluded and binding review between the parties? b) Since the reviewed rent figure specified by the appellant in Mr Choi's 27 September letter is in fact lower than the figure stipulated in the January 2003 lease, is the appellant's 27 September notice invalid because it proposes a rent outside the range contemplated by cl 2.2.1?The arbitration[21] By agreement dated 9 July 2007, the parties submitted their dispute for award and decision to Mr AR Galbraith QC as sole arbitrator. [22] Mr Galbraith heard evidence from the parties who were represented by counsel. The witnesses before Mr Galbraith included Mr Choi and Mr Neilson, who is responsible for the respondent's lease dealings. [23] Mr Galbraith's award was released on 8 May 2008.[24] The arbitrator dealt first with whether the landlord's notice issued under cl 2.1 was ineffective. The appellant had submitted that cl 2.2.1 prescribed upper and lower limits. Thus, to be effective, the rent proposed in a landlord's notice must comply with lease terms. [25] The arbitrator observed that the authorities dealing with errors in lease notices were not particularly helpful since the error was the landlord's. The tenant, instead of being prejudiced, had been advantaged. [26] The arbitrator turned to the issue, in terms of cl 2 of the lease, of whether the landlord was constrained to specifying a current market rental within the upper and lower limits stipulated in cl 2.2.1. The arbitrator referred to two authorities. The first was the High Court judgment of Stiassney v ANZ Banking Group (New Zealand) Limited (HC AK M1132/95 26 February 1996, Robertson J), to the effect that when giving notice under cl 2.1(a), a landlord was permitted to specify a rental which he considered to be the current market rental at the review date. [27] The arbitrator next referred to the English Court of Appeal judgment,Centrovincial Estates Plc v Merchant Investors Assurance Co Ltd (1983) The Times LR March 8th 1983, 168. That case, similar to the situation here, involved a landlord's solicitors writing to defendant tenants inviting them to agree to an annual figure of £65,000 as the appropriate rental value at the review date. This proposal was accepted the next day. Shortly afterwards, a partner in the firm of solicitors telephoned the tenant to say their letter contained an error and that what the landlord had intended was to propose a rent review at a higher figure of £126,000. In a subsequent summary judgment context, the Court of Appeal considered it was contrary to well established principles of contract law to suggest an offeror could withdraw an unambiguous offer after it had been accepted merely because there had been a mistake. [28] The arbitrator concluded:I am satisfied that there is no sufficient reason to interpret clause 2.1(a) and (b) other than as they read. Accordingly, in my view, the notice dated 27 September 2005, given by the landlord, is not outside the terms of the lease and therefore not invalid.[29] The arbitrator next considered the applicability of the Contractual Mistakes Act 1977. He held that steps taken by the parties under clauses 2.1(a) and (b) of the lease were merely the application of a previously agreed contractual process and did not involve any variation or collateral agreement. Thus the Act had no application. Counsel appear to have accepted that finding. It was not argued on appeal. [30] The final issue dealt with by the arbitrator was whether it was possible for the landlord to invoke restitutionary principles to remedy its mistake. Of relevance to this issue is the arbitrator's factual finding about the evidence of Mr Neilson who suggested that, when he received the 27 September 2005 notice, he realised the appellant had based the figure on the reduced rental rather than the contractual rental. [31] However, Mr Neilson's evidence was that he thought the figure was explicable as an intention of the landlord to provide some compensation for deficiencies in the standard of service in premises management about which the respondent had been complaining. On this aspect the arbitrator found:It was apparent from the evidence of Mr Choi, which I accept, that the terms of the notice dated 27 September 2005 were the consequence of a mistake arising from his lack of knowledge of the circumstances under which the lease had been entered into. Mr Neilson, who was responsible for the tenant's dealing with the lease, gave evidence that when he received the notice he realized that the landlord had based his claim on the reduced rental not the contractual rental. However, he said that he thought the reason for this was the landlord's intention to provide some compensation for deficiencies in the management and state of the premises which the tenant had been complaining about. While there was evidence of the tenant making such complaints, this justification for the tenant's belief when it received the 27 September 2005 notice did not appear in the initial response to the landlord's subsequent notices and then only when the tenant's lawyers had become involved. As well, it would be surprising for the tenant to draw this conclusion when no such suggestion appears in the landlord's notices and the tenant had been complaining of the landlord's indifference to the matters which it had raised. Certainly Mr Neilson may have thought at the time that the landlord's mistake was, in a sense, poetic justice given the tenant's concerns about the state of the premises but I do not accept that Mr Neilson believed that the landlord intended to reduce the rent below that which it was contractually entitled to claim. In short, I am satisfied that Mr Neilson realized that the likelihood was that an unintended error had been made in the 27 September 2005 notice.[32] The arbitrator, with reference to Winkelmann J's judgment in Villages of New Zealand (Pakuranga) Ltd v Ministry of Health (2006) 8 NZBLC 101,739 statedat [98] that New Zealand courts had stopped short of recognising any general restitutionary right founded solely on the basis of an unjust enrichment. [33] The arbitrator perceptively commented that, in general terms, a restitutional remedy was difficult to apply in a situation where the mistake is made in the performance of a contractual process. The mistake did not by itself subvert the contractual obligations or process. It was "in a sense self-contained within the landlord's camp" and was the type of error to which the Contractual Mistakes Act did not extend. [34] The arbitrator's conclusion was that the appellant's 27 September 2005 letter was a valid notice of the reviewed rent which the respondent accepted by payment of the reviewed monthly figure on 1 October 2005. That completed the contractual review process.Discussion[35] The parties' arbitration referral permitted an appeal to this Court on any question of law arising out of the award.[36] The appellant's amended notice of appeal poses two questions of law:a) Was the notice of 27 September 2005 served by the plaintiff on the defendant ineffective because it claimed a reviewed rental that was lower than the rent reserved by the lease between the parties and therefore inconsistent with clause 2.1(b) of that lease, amended by clause 2.1.1 of the Second Schedule to the lease?b) Was the arbitrator correct to refuse the plaintiff a remedy founded on the unjust enrichment of the tenant, unjust enrichment being available to the plaintiff either as an independent cause of action or as a basis of rectification?[37] The respondent, for its part, cross-appealed by posing one question of law which was:Was the plaintiff estopped and/or debarred from claiming a rental different from that contained in its notice of a rent review dated 27 September 2005 served by the plaintiff on the defendant?[38] During the course of the hearing I pointed out to Mr Marsh, who seemed to accept, that if both the appellant's questions of law were answered in the respondent's favour, there would be no need for me to answer the question posed by the cross-appeal. [39] Mr Dugdale's succinct and cogent submissions put greater emphasis on the second of the appellant's questions of law being, perhaps, a shift of emphasis from submissions made to the arbitrator which had clearly emphasised the mistake lying behind the appellant's 27 September notice. [40] Counsel classified his submission on the landlord's notice as an alternative to the unjust enrichment issues bundled up in the appellant's second question of law. He categorised it as "highly technical". His submission was the 27 September notice was ineffectual because the rent it proposed was lower than the minimum provided by the cl 2.2.1 ratchet provision. [41] The arbitrator had rejected that argument by holding that there was nothing in the lease which ruled out the landlord nominating a rent less than the stipulated minimum or greater than the specified maximum. The provisions of cl 2.2.1 only applied in a situation where cl 2.1(b) came into play and there was a dispute over the quantum of the current market rent. Mr Dugdale's submission was that such an interpretation might be flawed since, if a landlord were to nominate a rent "wildly in excess of a stipulated maximum" and the tenant took no steps (such as by leaving the landlord's notice on a mantle piece and overlooking it) then, in terms of cl 2.1(c), the excessive sum would become the new rent. Surely the parties to the lease did not intend such a result? [42] In my judgment, the arbitrator dealt correctly with the issue of the validity or otherwise of the appellant's 27 September 2005 notice. The rent review provisions contained in the lease are clear and unambiguous. The first step is the issue of a landlord's written notice under cl 2.1(a). The clauses, to a large extent, arefavourable to the landlord. Although notice cannot be given earlier than three months before the review date there is no other temporal restriction on the landlord. If the landlord (as frequently used to be the case) overlooks a date, the right to propose a new annual rent is reserved. Clause 2.1(a) and (d) in combination give a six month period of grace to the landlord to invoke the notice procedure. Even outside that six month period of grace, notice can be given at any time up to the next review date. [43] The agreed review mechanism reserves to the tenant a strict 28 day period to dispute the landlord's figure. Such a dispute must be notified. But if there is no notified dispute then the tenant is deemed to have accepted the landlord's proposed figure (cl 2.1(c)). [44] There is, in my view, no scope to place lower and upper limits on any current market rent the landlord may propose in its cl 2.1 notice. Certainly the cl 2.2.1 amendment to cl 2.1(b) contains a ratchet provision favourable to the landlord. It also places a ceiling on the review rent favourable to the tenant tying it to cumulative percentage increases in the CPI. [45] Obviously cl 2.2.1 places legal restraints on the parties. Even if current market rentals were to decline during the first three years, a tenant could not contend in any cl 2.2. arbitration or valuation referee determination that the rent should fall below that payable at the beginning of the lease. Nor could a landlord rely on a buoyant rental market to claim a rent review in excess of a figure produced by the CPI formula. But those practical restraints do not, in my judgment, lead to the inevitable conclusion that a landlord's notice under 2.1(a) is invalid or ineffective because its specified figure strays below or above the cl 2.2.1 boundaries. [46] On the appellant's first question I thus conclude that the arbitrator was correct and that the answer is "No". [47] Mr Dugdale's second submission, on the issue of whether the arbitrator was correct to refuse the appellant a remedy founded in unjust enrichment, relied, andproperly so, on the arbitrator's finding (supra [31]) that Mr Neilson had realised the likelihood of an unintended error in the 27 September notice. [48] Although accepting that New Zealand courts had been hesitant to found a cause of action for unjust enrichment in cases of this type, counsel considered it was time for a New Zealand court to "take the plunge" and suggested I should do so. [49] Here, submitted counsel, there had been an error in the first step of the contractual machinery. It should thus remain open to the appellant to correct the figure he had mistakenly nominated. Hypothetically, for instance, had a landlord mistakenly written "$10,000" rather than "$100,000" there must be a right to rectify the mistake. [50] In that regard counsel relied on the Court of Appeal's judgment in N B Hunt & Sons Ltd v Maori Trustee [1986] 2 NZLR 641. I do not consider that authority advances matters much. It involved a rent review which was to be based on a valuation of land. The Maori Trustee had calculated a reviewed rent in a letter the Court of Appeal described as "precise, unambiguous, and unqualified" (at 655). There was no evidence as to whether the recipient of the letter was aware of the true position. (The Maori Trustee's letter was based on a valuation of only part of the relevant land rather than the whole of it.) Issues of estoppel had been raised. The case was remitted back to the to High Court for further evidence. [51] Mr Dugdale relies on the case as authority for the proposition there can be no estoppel where a tenant is aware of the mistake because the latter's awareness negates any reliance on the representation. [52] On the facts before the arbitrator estoppel does not arise. The respondent does not have to rely on estoppel to prevent the appellant from trying to correct Mr Choi's mistake and issuing a subsequent cl 2.1(a) notice. Because the notice is valid and the reviewed rent was accepted, it is quite simply too late to restart the review mechanism and change the figure.[53] Mr Dugdale was on more interesting and perhaps stronger ground when he referred to the equitable jurisdiction to provide relief from the consequences of mistakes. Counsel accepted that in New Zealand such jurisdiction had been replaced in a contractual context by the Contractual Mistakes Act. Nonetheless in other areas courts retained the power to set aside a document or rectify it. [54] Gibbon v Mitchell [1990] 1 WLR 1304, 1307 and Dent v Dent [1996] 1 WLR 683 provided such examples, as did Sieff v Fox [2005] 3 ALL ER 693. In Gibbon v Mitchell relief was granted in respect of a voluntary and indeed unempowered surrender of a protected life interest under a marriage settlement. The surrender had the unintended consequence of vesting. In Dent v Dent a voluntary transaction (granting a family member rent-free exclusive occupation for life) had an unintended and unforeseen consequence under English legislation and could be set aside. Sieff v Fox involved the unintended consequence of the exercise of a discretion under a trust. [55] With reference to In re Butlin's Settlement Trusts [1976] 1 Ch 251, counsel argued this power of rectification extended beyond mistakes made by donors, or by settlors under deed polls and voluntary settlements. [56] These are all Chancery cases involving voluntary arrangements or dispositions, motivated, for instance, by inheritance tax considerations, where the arrangement has resulted in unintended adverse consequences. Rectification has followed. [57] In my judgment the cases are not analogous. The parties here were operating under agreed terms of a commercial lease. They were not negotiating on a voluntary basis under the umbrella of a trust or settlement. They had not arrived at a result which had a totally unforeseen consequence such as giving a tenant a statutory interest (as in Sieff) or creating vested interests (as in Gibbon). There was no unforeseen consequence of the type contemplated in the English cases which led to rectification. Rather there was an unfortunate error in a figure used. The consequence of sending out a cl 2.1(a) notice under the review mechanism wasperfectly clear to Mr Choi. So too was the consequence clear to the respondent of not disputing the figure. [58] A second and closely related argument was advanced of unjust enrichment which, Mr Dugdale submitted, underpinned many equitable remedies where monies paid by mistake could be recovered. Counsel did not dispute the arbitrator's comment that unjust enrichment is not yet available as an independent remedy in New Zealand. There is ample authority for such a conclusion. (See Equiticorp Industries Group v The Crown [1996] 3 NZLR 586, 611, per Smellie J; Rod Milner Motors Ltd v Attorney-General [1999] 2 NZLR 568, 576; Villages of New Zealand (Pakuranga) Ltd v Ministry of Health (op cit)). [59] As Lord Browne-Wilkinson said in Woolwich Equitable Building Society v Inland Revenue Commissioners [1993] AC 70, 196-197:Although as yet there is in English law no general rule giving the plaintiff a right of recovery from a defendant who has been unjustly enriched at the plaintiff's expense, the concept of unjust enrichment lies at the heart of all the individual instances in which the law does give a right of recovery.That dictum may provide a sign post to a road which is yet to be travelled. As stated in Burrows, Finn & Todd, Law of Contract in New Zealand (3 rd ed 2007) at 2.3.4:Much work remains to be done in this area of the law. It will take a long time for the Judges, no doubt with appropriate prompting from the writings of academics and others, to mould the current complex mass of precedent into a coherent whole. The challenge is to tease out a set of consistent principles without losing sight of the important fact that the various circumstances in which a plaintiff can recover from a defendant differ greatly. Some fear that too ready a use of unjust enrichment may cloud those very real distinctions. Nor is it clear beyond argument that "unjust enrichment" provides a suitable explanation of all the traditional grounds for recovery of money.[60] Beguiling though Mr Dugdale's invitation may be to "take the plunge", I am far from satisfied this is an appropriate case. Although the arbitrator found that Mr Neilson, when he received the 27 September notice, realised "the likelihood" that an unintended error has been made, the context and circumstances of that error do not engage my conscience to the extent that I feel obliged to craft a remedy based on unjust enrichment. The respondent has arguably been "enriched" to the extent thatthe concessional rent negotiated for the first three years of the lease has, with only CPI adjustments, been carried across to the second three years of the term. But in my judgment it will not always be inequitable or unfair for one commercial party wittingly to latch on to and take advantage of sheer carelessness on the part of another commercial party. It would need a clearer case than this to categorise the windfall to the respondent as unjust. And in any event, the windfall was a modest one. The appellant still had the assurance of the rent which, although arguably below the market, had been satisfactory to it, whereas the respondent for its part had to endure what is clearly a diminution of the standard of services provided. [61] The strongest authority on which counsel relied was Cressman v Coys of Kensington (Sales) Ltd [2004] 1 WLR 2775, a decision of the English Court of Appeal. [62] The case involved the purchaser's refusal to relinquish a personalised number plate worth £15,000 on a car which he had purchased. At the outset the purchaser had been informed he was not entitled to the plate. [63] The vehicle's auctioneers became a litigant, although it is not necessary to sketch the background. At first instance the Judge found that the purchaser had been unjustly enriched by receiving a benefit in the form of the personalised plate which he knew or ought to have known he was not entitled to have. [64] The Court of Appeal held that where unjust enrichment was alleged, four questions arose: i) Had a defendant benefited or been enriched? ii) Was the enrichment at the expense of the claimant? iii) Was the enrichment unjust? iv) Was there any specific defence available such as a change of position?[65] The Court held that justice required a person who, as the result of some mistake made in the execution of an agreed bargain, had the benefit or the right to a benefit for which he knew he had not bargained or paid, to reimburse the value of that benefit back to the other party. [66] Mance LJ stated:[37] Looking at the matter generally, I have no doubt that justice requires that a person, who (as a result of some mistake which it becomes evident has been made in the execution of an agreed bargain) has the benefit or the right to a benefit for which he knows that he has not bargained or paid, should reimburse the value of that benefit to the other party if it is readily returnable without substantial difficulty or detriment . A person who receives another's chattel must either return it or pay damages. However, [the purchaser's] insistence on keeping the [number plate] and the absence of any obvious means of compelling its retransfer are reasons for analysing this case in terms of unjust enrichment.[67] The case is clearly distinguishable. The mistake being referred to inCressman was clearly, in context, the mistake of allowing the purchaser to retain the number plate of the car he had purchased. The Court permitted the concept of unjust enrichment to be used here as a sword to compel the purchaser to disgorge the value of property to which the contract of purchase did not extend. [68] Here the contract (the lease) and the rent review mechanisms are clear. For the reasons already given the appellant cannot contend that the respondent, on these facts, is retaining property or some benefit to which it has no entitlement. It is not possible, in the context of the lease mechanism, to conclude that the respondent has had a benefit which was not part of the "bargain." [69] Like the arbitrator I retain some uneasiness about the inevitable result given Mr Neilson's realisation that an unintended mistake had probably been made. However, these are commercial parties bound by a commercial lease. In the sometimes ruthless world of commerce there is no prohibition on one party taking advantage of another party's unwitting mistake and indeed no sound policy reason why the law should not permit outright and repeated carelessness to confer an unexpected and unintended advantage.[70] My conclusion is the arbitrator addressed the issues correctly before him. The appellant's second question of law must thus be answered "Yes".Result[71] The result of this appeal is thus: a) To the appellant's first question of law (supra [36]) the answer is no. b) To the appellant's second question of law (supra [36]) the answer is yes. c) To the respondent's question of law raised in the cross appeal (supra [37]) no answer is required.Costs[72] The appellant, having failed in this appeal, is liable to costs. Costs are reserved in the unlikely event of the parties not being able to resolve the issue. The appropriate band would be 2B........................................... Priestley J