Judgment Lord Justice Rimer : Introduction 1.                  This is an appeal against a decision on an assessment of damages for trespass made by Deputy Master Matthews on 25 February 2009. The assessment was made pursuant to the order dated 21 February 2006 made by Mr Launcelot Henderson QC (as he then was), sitting as a Deputy Judge of the High Court in the Chancery Division. His order followed a trial between the parties raising issues in the nature of a boundary dispute. The claimant, Fair Acre Investments Limited (‘Fair Acre’), was successful in the trial and by paragraph 5 of his order the Deputy Judge directed an inquiry as to the mesne profits and interest that the defendants must pay Fair Acre in respect of their trespass on its land for the five-year period from 1 June 2001 to 31 May 2006. The defendants are Earlrose Golf & Leisure Limited and Ethos Environmental Limited (formerly Sweeney Environmental Limited). 2.                  The Master held that the defendants must pay Fair Acre £170,325 by way of damages, plus interest of £34,065. He arrived at that conclusion by holding that the base rental value of the land at the agreed valuation date of 1 June 2001 was £5.00 per square foot (‘psf’), to which figure he then applied various discounts. The defendants had argued for a materially lower base value not exceeding £1.75 psf. The Master gave them permission to appeal, limited to the correct base value, expressing the view that their arguments against the correctness of his decision on that issue could not be dismissed as fanciful. Success on the appeal would represent a major saving to the defendants, section 7 of their Appellants’ Notice inviting a substitute assessment (including interest) of £64,632. 3.                  Mr Wayne Clark appeared before us for the appellants/defendants, and Mr Alexander Hill-Smith for Fair Acre. Both also appeared before the Master. The facts 4.                  The subject land comprises two parcels of open land at West Drayton, in the London Borough of Hillingdon. They are part of a greater area of scrub land owned by Fair Acre called The Lizzards. The more northerly of the two parcels is wedge shaped, has been called ‘Area A’ and measures some 3,465 square feet. The more southerly parcel is rectangular, runs east from (approximately) the thin end of the wedge represented by Area A, has been called ‘Area B’ and measures some 5,672 square feet. Area A is at a uniform level throughout, having been so levelled by the defendants, whereas Area B is in part at the same level and in part (some 2,335 square feet) at a higher level. Access to the higher area can only be obtained by the use of a ladder or stairs. 5.                  The two areas are adjacent to land owned by the first defendant, Earlrose, known as the Trout Lane Depot (‘the depot’). The second defendant, Ethos, is the lessee of the depot, holding under a lease dated 8 February 2000 granting a 20-year term from 1 February 1997. The defendants are part of a group of companies controlled by Mr John Sweeney which carry on the business of a waste recycling centre at the depot. By the commencement of the relevant five-year period, they had incorporated both Areas A and B into the land they used for that business. They stored plant and equipment on parts of those areas and waste materials on other parts, including the higher level of Area B. By the end of the assessment period, all such use had ceased, an exercise requiring a major dismantling and removal exercise performed by the defendants at considerable cost. Despite the apparently valuable rental value that the Master attributed to the two areas, we were told that since the defendants vacated them in 2006 they have remained unused. 6.                  Whilst there is more than one way in which, in a trespass claim, mesne profits may be assessed, Fair Acre elected at the assessment hearing for one based on the ordinary letting value of the two areas. In applying such method, it is not necessary for the claimant to prove that he could or would have let the land to someone else had the defendant not trespassed on it; and any gain that the defendant achieved by his trespass is left out of account. As the Master put it, ‘one looks to the thing, and not to the person’. 7.                  Such an inquiry may not be difficult when assessing the letting value of 75 Acacia Road. The combination of various features of Areas A and B made the exercise before the Master more difficult. Both areas are isolated, sandwiched between the western side of the defendants’ land at the depot and the remainder of Fair Acre’s land. They enjoy no direct access from the public highway. Access can only be obtained over the defendants’ land (the easier option) or over Fair Acre’s remaining land (the more difficult and potentially expensive one, as it would require the construction of a new roadway). In addition, the two areas had no planning permission for waste recycling activities; part of Area A was burdened by a restrictive covenant dating from 1903 which (if enforceable) might prevent such activities; and both areas were affected by an injunction granted on 24 June 1996 relating to tipping activities on The Lizzards in breach of planning control which, unless varied, prevented the lawful extension of the defendants’ business to Areas A and B. The injunction did not extend to the depot, upon which the defendants’ activities had always been lawful. The hearing before the Deputy Master 8.                  The Master had the benefit of expert valuation evidence adduced by Fair Acre from Michael Donaldson, a chartered surveyor. The defendants adduced factual evidence from Mr Sweeney and expert valuation evidence from Peter Bellion, also a chartered surveyor. Both experts had prepared reports and were cross-examined. Mr Bellion’s case in his report was that the compensation should be fixed on the basis of what Fair Acre and the defendants would have negotiated by way of a licence fee for a five-year licence, which he considered would be no more than a nominal fee. When, however, Fair Acre elected at the hearing for an assessment on the basis of the open market letting value of the subject land, Mr Bellion gave evidence as to his opinion on that basis, one to the effect that the value should be assessed on the basis that all the problems relating to the two areas that I have summarised had a depreciatory effect on the value, whereas Mr Donaldson disagreed, on the ground that the defendants had used both areas without difficulty during the relevant period. Both experts relied on comparables in support of their opinion as to the letting value of the subject land. It is the use that the Master made of them that is at the heart of the appeal and so I must explain them. Before doing so, I comment that I regard it as unsatisfactory that it was not until the hearing that Fair Acre made its election as to the basis on which the compensation was to be assessed. It appears to me to be obvious that the fair disposal of an assessment such as that before the Master required the election to be made well in advance of the hearing so that the defendants’ expert should have proper notice of the considerations to which to direct his expertise. 9.                  Mr Donaldson relied on two comparables: Holloway Quarry, Holloway Lane, Harmondsworth, Sipson; and a former Gas Works site at Brent Road, Southall. Mr Bellion also relied on two comparables, being leases from British Waterways Board (‘BWB’) of two small rectangular parcels of land lying alongside each other and to the north of, and abutting, the depot into which they are now incorporated. The westerly parcel also abuts the northern end of Area A. These two parcels were called ‘the Green Land’ (to the east) and ‘the Blue Land’ (to the west). Holloway Quarry 10.              This site (which had been found by Fair Acre rather than Mr Donaldson) is used as a waste recycling facility. Mr Donaldson relied on a lease of it creating a tenancy at will taking effect from 24 November 2008. The lease showed a basic rent of £150,000 a year, or some £8.00 psf, plus a turnover rent based on the number of skips exceeding 500 a year delivered to the site. The business carried on at the site is comparable to that carried on at the depot. The site was closer to the motorway than the depot and Mr Donaldson accepted in cross-examination that it had ‘far better access’ than the depot. The Master considered that the site may have enjoyed advantages not present in relation to Areas A and B. The Gas Works 11.              Mr Donaldson explained in his report that he had also looked at open storage sites in the vicinity. This took him to a tarmac site, formerly a Gas Works site, used for car-parking in connection with Heathrow Airport. The landlords charge approximately £60,000 per acre, or £1.38 psf, although if the area let is less, for example a third of an acre, the rent rises to about £2.00 psf. There was no written evidence of this letting. As with Holloway Quarry, the rents quoted were also from 2008. This area was simply available for use for storage, not light industrial use. Mr Donaldson’s opinion was that as the subject land was used as part of the defendants’ waste recycling station, it was significantly more valuable to them than mere storage land. He agreed in cross-examination that car-parking was of substantial value. 12.              Mr Donaldson’s report, remarkable for its economy (occupying barely two pages), did not trouble to explain how rents achieved in 2008 (in the case of the Holloway Quarry, November 2008) might assist the Master in determining a letting value as at 1 June 2001. That omission rendered his report of questionable value. He was perhaps fortunate to be given the chance of explaining himself in his oral evidence, his explanation then being that although the market had risen since June 2001, it had then also fallen, so resulting in the 2008 figure being a good representation of 2001 values. He did not, however, support that assertion otherwise than by reference to his own experience: he produced no concrete evidence to support it. He also did not know whether the Holloway Quarry tenancy included equipment already on the site, something he had not considered. The Green Land 13.              This is an area of about 2,250 square feet let in 1982 on a 42-year lease from 24 June 1980 with five-year reviews and since occupied as part of the depot. The lease is now held by Earlrose. The June 2000 rent review resulted (in 2001) in an agreed reviewed rent of £4,850 per year, or £2.15 psf. The Blue Land 14.              This is also an area of about 2,250 square feet. In September 2000 the BWB granted a Sweeney group company a 23-year lease at an annual rent of £3,000, or £1.33 psf, with five year reviews. The first rent review was in 2005, when the outcome of the review negotiations was that the rent was not increased. 15.              There was no explanation why adjoining areas of like size, both forming integral parts of the depot, should have such significantly different rents. The experts’ opinions 16.              Mr Donaldson favoured a rental value for Areas A and B of £7.00 psf for the lower level and £3.50 for the higher level. His figures reflected no depreciation for the access difficulties or the other disadvantageous features of the two areas that I have listed: his view was that they were irrelevant as the defendants had used both areas throughout the five-year period. Mr Bellion’s primary case had favoured a nominal rental value of, say, £100 per year for both areas but, on the basis that he was looking for the open market rental value of the subject land, he would have started with a rent of £1.75 psf (an average of the rents fixed in or as at 2000 for the Green Land and the Blue Land) and would then have discounted that figure to reflect the disadvantages affecting areas A and B. The Deputy Master’s decision 17.              The Master’s view was that the access problem would, and that the other problems could, have a depreciatory effect on the letting values of the subject land. A prospective user would take them all into account in assessing the risk they represented and would price the land accordingly. In valuing the land, it was not, however, sufficient to consider merely the position of a third party wishing to use it himself. He would also know of the existence of the defendants, who were carrying on their business in adjacent land and who could be regarded as in the position of special purchasers. The third party might be prepared to pay more for the subject land in the thought or belief that he might be able to dispose of it to them, since it would be likely to be more valuable to them than to a new user. The increased value he would be prepared to pay would be somewhere between the price the third party would pay for his own use and the price the special purchaser would pay. It appears that the Master was, therefore, of the view that he had to consider not just what a third party would pay for the land for his own use, but what a speculator aware of the existence of the defendants might pay for it. It is, however, unclear that the Master actually engaged in any such consideration when making his decision. 18.              The heart of the Master’s reasoning for his decision is in paragraph 31 of his judgment, as follows: ‘I turn to the question of value itself. First I must assess the value of the land on the basis that access is available (as it is to the Defendants). In my judgment the £8 psf obtained for Holloway Quarry is too high for Areas A and B. Too much is different from those areas, and I am troubled by the simple equation of 2001 and 2008 values by saying that the market went up and then down again, without any statistical backup. Mr Donaldson himself recognised that it was not directly applicable, in giving a value for Areas A and B of £7.00 psf. On the other hand, the averaged value of £1.75 for the Blue Land and the Green Land seems too low. The Defendants agreed with the BWB a rent review figure in 2001 of about £2.15, and it is hard to see why a lower figure (about £1.33) was agreed by the BWB for the Blue Land. But even £2.15 seems too low when looking at Holloway Quarry, which is after all land used for a similar business purpose, and when looking at the figure of £2.00 for smaller areas quoted in connection with the Gas Works site (which is just used for storage, not for light industrial use).’ 19.              The Master concluded therefore that the true figure lay between £2.15 and £7.00 psf; and he fixed on £5.00 psf as the figure fairly reflecting what he called the base value of the subject land as at 1 June 2001. To that figure he then applied a discount of 50% in respect of the higher part of Area B; a discount of 5% to reflect the risks associated with the lack of planning permission for both areas and the restrictive covenant affecting part of Area A; and a discount of 10% to reflect the access problems. The effect of the discounts was that he arrived at a figure of £4.28 psf for the lower parts of areas A and B and £2.14 psf for the higher area. The appeal 20.              For the appellants, Mr Clark submitted that the Master was wrong to find that the base value was £5.00 psf before applying his deductions. He said the comparables did not enable him to arrive at such a figure. No comparable supported it. The best evidence was that derived from the BWB lettings which proved base figures of £1.33 psf and £2.15 psf for the Blue and Green Land respectively. The former rent was determined in September 2000, nine months before the agreed valuation date; the latter rent was agreed in 2001, but presumably as at June 2000, a year before the valuation date. Mr Clark’s assertion was that the Master should have started with those figures as representing the governing comparables and then applied the discounts that he did. 21.              As for the Holloway Quarry transaction, Mr Clark said the Master should not have placed any weight on it. He had correctly recognised that, absent any supporting evidence making good the point, a November 2008 rental value could not be relied upon as indicative of June 2001 values. He should therefore simply have rejected the Holloway Quarry comparable. To the extent he did rely upon it, it was irrational to do so, particularly when he was also provided with true comparable evidence from 2000 in the form of the BWB leases. Moreover, Holloway Quarry concerned a different type of business. It was a self-contained unit, which the Master recognised may have included extra advantages to the tenant that were not present in relation to areas A and B. These included that the tenant could dispose of waste in the adjoining quarry, whereas the tenant of the subject land would be required to incur costs of disposal which were not being incurred by the tenant of Holloway Quarry. In addition, Holloway Quarry was, according to the lease terms, a ‘turn key’ operation, with all equipment provided by the landlord. This was the opposite of the situation applying to the subject land. Mr Clark also pointed out that the Master failed to give any weight to Mr Bellion’s evidence – derived from the landlord and supported by an email exchange – that the Holloway Quarry transaction was a confidential one and was not an arm’s length negotiation. 22.              Mr Clark submitted that the Gas Works was an equally useless comparable. It too was said to reflect a 2008 value, not a 2001 one, and there was no documentary evidence of the terms of the letting. The site was used for car-parking in connection with Heathrow Airport, which Mr Donaldson accepted was of substantial value. 23.              The Master was, Mr Clark submitted, therefore wrong to place any reliance on Mr Donaldson’s comparables and to reject the BWB comparables. He was, it was said, further wrong to approach the assessment exercise on the basis that he had to seek a value ‘somewhere between the price the third party would pay for his own purposes, and the [greater] price which the special purchaser would pay’ (paragraph 13 of the judgment). There was no evidence of any speculator being in the market on the valuation date and so this was a mistaken approach. He ought to have approached the assessment on the basis that the market value was no greater than that which a third party would pay for his own purposes. He was yet further wrong to fix a rent for the higher level at area B at £2.50. This was scrub land to which access could be obtained only by utilising some form of ladder or stairs, yet the Master’s figure of £2.50 was a higher value than a 2008 value for flat, tarmacadamed land, with easy access and used in connection with parking at Heathrow. 24.              As to what the Master should have done, Mr Clark submitted that he should have found that the best evidence of the open market letting of the land to be the BWB transactions. They were of land directly comparable to the subject land in terms of location and the use to which it was put. There was no basis for rejecting this evidence or for any conclusion that the transactions were other than at arm’s length. The rent under those leases was fixed in or as at 2000, the year before the valuation date, and although the rent so fixed was for terms longer than the five-year period, an adjustment could be made to take account of this. 25.              Having taken the BWB transactions as his starting point, the Master should have taken the average of the two rents they reflected, or £1.75 psf, as the maximum starting figure. Mr Clark accepted that the higher part of Area B should, as the Master held, be valued at half that, and he also accepted the discounts of 5% and 10% that the Master applied to the resultant figures to reflect the planning and restrictive covenant risk and the access problems. Mr Clark would, however, also apply a further 10% discount to arrive at a rental value appropriate to a five year term rather than the long terms of the BWB leases. The net result of the adoption of this approach is a figure totalling £10,770.50 per year for the subject land. 26.              For Fair Acre, Mr Hill-Smith submitted that the rental value found by the Master was a finding of fact that this court should not disturb. He said the Master was correct to direct himself that he was not bound to choose between the two, very different, approaches of the experts. The Master noted the shortage of comparable transactions before him but said he was doing his best on that evidence, which was a proper approach. If, said Mr Hill-Smith, there was anything surprising about the outcome of the hearing before the Master, it was the giving by the Master of permission to appeal. 27.              To the extent that the Master placed reliance on Mr Donaldson’s evidence, he was entitled to do so. No suggestion was made that Mr Donaldson lacked relevant experience or expertise. It was for the Master to decide how much weight to place upon his evidence. Mr Bellion had, by contrast, persisted in the case that the mesne profits should be no more than a nominal £100, a case which the Master did not accept and which is not raised on the appeal. His report referred to no comparables or other valuation evidence (although I have explained how Mr Bellion did rely at the hearing on the BWB comparables). 28.              Mr Hill-Smith submitted further that to the extent that the Master relied on the Holloway Quarry comparable, he did not do so uncritically. He was concerned that it was a 2008 transaction and he recognised the differences with the subject land. He was not, however, bound to treat this evidence as wholly worthless. He was similarly aware of the differences between the Gas Works site and the subject land and was similarly not obliged to reject this comparable as worthless. 29.              As for the BWB leases, Mr Hill-Smith said the evidence relating to the relevant transactions was exiguous. Each lease provided for five-year reviews. Whilst the Master referred in paragraph 20 of his judgment to the agreement in 2001 for a review to £4,850 of the rent for the Green Land as from 1 June 2000 (£2.15 psf), this information derived exclusively from paragraph 22 of Mr Sweeney’s third witness statement. There was no evidence of how the reviewed rent came to be agreed. 30.              As for the Blue Land, this was the subject of an original lease in 2000 at a rent of £3,000 a year (£1.33 psf). Mr Hill-Smith devoted part of his argument to a reference to a meeting in 2006 between Mr Sweeney and Mr Casey as to the first review of the rent, which does not appear to me to be of direct assistance for present purposes. He also made the point that there was no evidence of how the initial rent of £3,000 came to be agreed in 2000. 31.              In any event, said Mr Hill-Smith, Mr Donaldson’s opinion was that the rental levels for the Blue Land and the Green Land were below market value and the Master effectively found that they were by rejecting the proposal that he should take their mean of £1.75 psf as the best guide to the value of the subject land. The Master was, in particular, mystified as to the difference between the rent levels of the two comparables; and, as there was no explanation of this, he was entitled to treat them with circumspection. 32.              If, contrary to his primary submission, this court were to take the view that the Master should have taken his lead from the rents obtained for the Blue Land and the Green Land, Mr Hill-Smith questioned why the Master should have taken an average figure of £1.75 psf. The £2.15 figure was agreed in 2001, at almost exactly the same date as the agreed valuation date. If he should have derived help from these comparables, that is the figure he should have used. 33.              As to the proposed 10% deduction for access difficulties, it is said that that was an illogical deduction because the two comparables each suffered from the same access difficulties as the subject land so that the rents achieved for them can be taken to have reflected that disadvantage. Mr Hill-Smith accepted that they both had planning permission. He did, however, also resist the further 5% deduction that the Master applied. 34.              Finally, as to Mr Clark’s proposed 10% discount for to reflect the length of the BWB leases as compared with the assessment period, Mr Hill-Smith said that the Master rejected this suggestion by Mr Bellion and was entitled to do so. A long lease, he said, was not always a benefit, particularly in circumstances where, as with the BWB leases, there is no break clause Discussion 35.              The Master’s decision under challenge is probably not accurately  characterised as a finding of fact so much as an evaluation of the factors adduced in evidence with regard to the rental value as at June 2001 of Areas A and B. In such cases, there will rarely be one right answer. There will instead usually be scope for legitimate disagreement as to what the right answer is. The evaluation exercise that the Master was undertaking was therefore analogous to the exercise of a discretion. Challenges before an appellate court to an exercise of discretion are of course approached with caution. They will usually only succeed if the judge is shown to have failed to take account of some material matter, or to have taken account of some immaterial matter, or to have arrived a decision which can fairly be assessed to have fallen outside the scope within which reasonable disagreement is possible and so to have been plainly wrong. A challenge to the type of evaluation that the Master was required to make in this case rests upon like considerations as those applicable to a challenge to an exercise of discretion (Assicurazioni Generali SpA v. Arab Insurance Group [2003] 1 WLR 577, [14] to [17], per Clarke LJ; and Datec Electronics Holdings Ltd and others v. United Parcels Service Ltd [2007] 1 WLR 1325, at [46], per Lord Mance). 36.              Whilst reminding myself of the caution with which an appellate court should venture to disagree with the decision of a judge arrived at after the type of evaluation exercise in which the Master had to engage, I have, with respect, come to the conclusion that the Master’s decision was plainly wrong. 37.              This was a case in which the correct approach to the determination of the rental value of the subject land as at June 2001 lay in proceeding by analogy with other transactions, that is by reference to comparables. It will be a rare case in which any comparable is a perfect match for the valuation exercise in issue. That is because the comparable will be unlikely to relate to a property with identical characteristics or to reflect a transaction effected at the same time. The most helpful comparables will be those whose characteristics are close to those of the subject property and in respect of which the transaction was also effected close to the material time. It will be for the tribunal to assess what help it can derive from them; and, as regards any comparable which it does regard as of assistance, to have regard to its different characteristics in making adjustments for the purpose of assessing the rental value of the subject land. The exercise will usually be heavily dependent on the help given by the expert evidence. 38.              In the present case the two comparables relied upon by Mr Donaldson by way of analogous transactions were, on the face of it, worthless. As the lapse of time between the transaction the subject of the comparable and the valuation date increases, so does the comparable become progressively unreliable as evidence of the rental value at the valuation date (probably a statement of the obvious, but see Segama NV v. Penny Le Roy Ltd [1984] 1 EGLR 109, at 112B, per Staughton J, for judicial support for it). Here there was a gap of some seven years between the valuation date and the two comparables, with no evidence corroborating Mr Donaldson’s assertion that (in effect) rental values in November 2008 were the same as they were in June 2001. If his opinion was sound, he must have been able to illustrate it. How could he have formed it save by the comparison of actual transactions? Yet Mr Donaldson produced no supporting statistical evidence. Faced with that omission, the Master did not accept Mr Donaldson’s assertion that the 2008 values equated to 2001 values. He made that clear in paragraph 31 of his judgment, where he also pointed out that, despite the fact that Holloway Quarry was used for like purposes as the subject land, ‘too much [about Holloway Quarry] is different from those areas’ and he said that even Mr Donaldson recognised that by proposing a base value for the subject land of £7.00 psf. 39.              That criticism of Holloway Quarry as a comparable would seem to me to put its consideration out of court. Yet the Master did not do so because he then compared its rent with the £2.15 psf achieved for the Green Land in 2001 and concluded that the latter rent must be too low. With respect, I regard that as having been irrational. Having rejected Holloway Quarry as a worthless comparable at the beginning of paragraph 31, the Master then relied upon it at the end of the same paragraph as requiring him to conclude that the £2.15 psf achieved at the 2001 rent review for the Green Land was too low. He also there relied upon the 2008 rent achieved for the Gas Works site, a comparable he must logically have regarded as equally worthless. It was again based on a 2008 figures, unsupported by documentation, and related to a different use, namely car-parking on a tarmac area used in connection with Heathrow Airport, a use that Mr Donaldson agreed was of substantial value. I fail to see how it was of any use to the exercise that the Master was performing. 40.              In my judgment, it is apparent that the BWB transactions represented the best comparables. They were in respect of leases of pieces of land forming part of the depot and used for the same purposes as that for which the subject land was used during the assessment period. The fact that there was no explanation of the difference between the rents for the two leases did not prevent them being the best comparables. It is true that they both reflected rents agreed in or as at 2000, up to a year before the valuation date; but we were not referred to any evidence that there had been a material change in values during that year. 41.              This was therefore a case in which the Master should have regarded the BWB transactions as providing the best guidance as to the base value for the subject land. He should have placed no reliance on Mr Donaldson’s evidence. Mr Donaldson sought to dismiss the BWB comparables by his unsupported opinion that they did not reflect the true market rent of the BWB land. That was a hopeless endeavour because there was no evidence that they were other than arm’s length transactions and thus the best evidence of the market rent. It was for Fair Acre to prove otherwise and it did not do so (compare Trans-World Investments v. Dadarwall [2008] 1 P. & CR 314, at [30], per Mummery LJ). 42.              In failing to have primary regard to the BWB transactions, and in instead adopting the view that the base rent for the level part of the subject land at June 2001 was over twice the market rent agreed for the Green Land at the 2001 review and some 3.75 times the rent agreed for the Blue Land in 2000, I consider that the Master fell into error. The consequence was that he arrived at a decision that I would regard as wrong. Neither counsel suggested that this court should remit the assessment for a re-hearing. If we considered the Master to have been in error, we were asked to assess the damages ourselves. 43.              As to that, we are necessarily at a disadvantage in doing so, because we do not have the benefit of the full flavour of the expert evidence given in the case. In particular, we do not have any evidence as to where, within the range of £1.33 to £2.15 psf reflected by the BWB comparables, we might fairly be able to fix the base value for the subject land. It follows, I consider, that we have little choice but to wield a broad axe (a tool well known to the law: see Watson, Laidlaw & Co Ltd v. Pott, Cassels, and Williamson [1914] 31 RPC 104, at 118, per Lord Shaw). For reasons given, I would disregard Mr Donaldson’s evidence in its entirety. The best guide as to the June 2001 rental value of Areas A and B is that derived from the two BWB transactions. Given the lack of evidence to which I have just referred, I do not consider that there is any basis upon which this court can favour one rate rather than the other, or decide that the true base rental value is other than the average figure for which Mr Clark contended, namely £1.75 psf (a rounded figure). I would therefore adopt £1.75 psf as the base value rental value. The next question is whether there should be applied to it the Master’s various discounts, namely, 50% for the higher part of Area B, 5% for the planning and restrictive covenant problems and 10% for access problems. 44.              I did not understand either counsel to disagree with the 50% discount in respect of the higher part of Area B and so I would apply that discount. Mr Hill-Smith objected, however, to both the 5% and the 10% discounts. I am not sure I followed the logic of his objection to the 5% discount, because he accepted that the BWB land had the requisite planning permission and I did not understand him to disagree with Mr Clark’s submission that it was unaffected by the restrictive covenant. As for the 10% discount, however, his position was that the BWB lands suffered the same access difficulties as the subject land, to which Mr Clark’s answer was that the BWB sites enjoy access via the canal which they adjoin. In addition to disagreeing with Mr Hill-Smith’s discount objections, Mr Clark also argued that there should be a yet further 10% discount to reflect the fact that we are only assessing the rental value for a five-year period, whereas the BWB rents were negotiated for five-year slices of long leases. 45.              There was some discussion as to whether, given the limited nature of the permission to appeal granted by the Master, it was open to either counsel to argue these additional points about the discounts, although neither objected to the other advancing the argument that he did. I would not rule out either argument. As we have reached the point at which we are assessing the damages afresh, I consider that we should take all relevant considerations into account. 46.              In my judgment, there is force in Mr Hill-Smith’s submission that the rents achieved in respect of the BWB leases must be assumed to reflect the access problem, to which I do not consider that the opportunity of canal access provides a complete answer. I would not, therefore, apply a 10% ‘access’ discount. I would anyway be disinclined to do so for my further reasons below as to why I would also disallow the other discounts for which Mr Clark contended. 47.              I accept that there can be said to be some logic in Mr Clark’s submission that the base value figure should be discounted by either 5% or some other appropriate percentage to reflect the fact that, unlike the BWB land, the subject land suffered from planning and restrictive covenant problems. Logical or not, I do not however propose to apply that discount. Nor would I reduce the base value by the further 10% discount to reflect the shortness of the notional letting of the subject land. My reason for declining to apply either discount is that I have arrived at the base value of £1.75 psf by a route supported by neither art nor science but simply by the application of a broad axe. I do not suggest that £1.75 psf, as opposed to almost any other figure between £1.33 and £2.15, must be regarded as the true base value; and, that being so, I am not satisfied that either of the two further refinements for which Mr Clark has contended is justified. It involves the application of a sophisticated refinement to a figure arrived at by a crude method of averaging and thus requires the adoption of an exercise that I would regard as artificial. It cannot be usual to refine with a scalpel that which has been produced by the wielding of an axe. Disposition 48.              I would allow the appeal, set aside paragraph 1 of the Master’s order and substitute an order which reflects the figures I have explained. If my Lords agree, I would hope that the parties will be able to agree a form of order. Mr Justice Kitchin: 49.              I agree. Lord Justice Jacob : 50.              I also agree.