(v) Benefit Realizable in Money
It remains unclear whether it is appropriate to consider a defendant to have been incontrovertibly benefited where the claimant has improved the defendant’s property, and so increased its value, but the defendant has not realized that benefit in money. Burrows considers that a benefit which is potentially realizable in money should be treated as an incontrovertible benefit, but only if it was reasonably certain that the defendant would realize the benefit.1 Judge Bowsher QC in Marston Construction Co Ltd v Kigass Ltd136 accepted that a realizable benefit can be considered to be an incontrovertible benefit.  This approach appears to have been supported by the Court of Appeal in McDonald v Coys of Kensington,138 although Burrows’ qualification of the realization being reasonably certain was rejected as being too restrictive.
But the conclusion that the defendant has been incontrovertibly benefited simply because he or she has received something which could be sold is generally unacceptable,1 because it unnecessarily subverts the autonomy principle. Analysis of all the other categories of incontrovertible benefit shows that, with the exception of the test of whether the benefit is realizable in money, the principle does not subvert the autonomy of the individual which underlies the principle of subjective devaluation. This is because, where it is proved that the defendant has received an incontrovertible benefit within one of these other categories, it is clear that either the defendant has no free choice to exercise as to whether to accept the benefit, as in the category of anticipation of necessary expenditure, or had exercised that choice, where the benefit has been realized in money or where the defendant has received property which he or she could return. The difficulty with the test of whether the benefit is realizable in money arises precisely because in that situation the defendant does have a free choice whether or not to accept the benefit, and there is no acceptable basis on which we can exercise that choice on the defendant’s behalf. Therefore, the better view is that this test of incontrovertible benefit should be rejected save, perhaps, where it is inevitable that the defendant will realize the benefit, for in such a situation there will be no free choice to exercise. Such inevitability will, however, be virtually impossible to prove.