"In my opinion the question whether a valuation is binding upon the parties depends in the first instance upon the terms of the contract, express, or implied. This was pointed out by Sir David Cairns in the Court of Appeal in Baber v Kenwood Manufacturing Co Ltd (at 181). A valuation obtained by fraud or collusion can usually be disregarded even in an action at law. For in a case of fraud or collusion the correct conclusion to be drawn will almost certainly be that there has been no valuation in accordance with the terms of the contract. As Sir David Cairns pointed out, it is easy to imply a term that a valuation must be made honestly and impartially. It will be difficult, and usually impossible, however, to imply a term that a valuation can be set aside on the ground of the valuer's mistake or because the valuation is unreasonable. The terms of the contract usually provide, as the lease in the present case does, that the decision of the valuer is "final and binding on the parties". By referring the decision to a valuer, the parties agree to accept his honest and impartial decision as to the appropriate amount of the valuation. They rely on his skill and judgment and agree to be bound by his decision. It is now settled that an action for damages for negligence will lie against a valuer to whom the parties have referred the question of valuation if one of them suffers loss as the result of his negligent valuation: Sutcliffe v Thackrah [1974] AC 727; Arenson v Arenson [1977] AC 405. But as between the parties to the main agreement the valuation can stand even though it was made negligently. While mistake or error on the part of the valuer is not by itself sufficient to invalidate the decision or the certificate of valuation, nevertheless, the mistake may be of a kind which shows that the valuation is not in accordance with the contract. A mistake concerning the identity of the premises to be valued could seldom, if ever, comply with the terms of the agreement between the parties. But a valuation which is the result of the mistaken application of the principles of valuation may still be made in accordance with the terms of the agreement. In each case the critical question must always be: Was the valuation made in accordance with the terms of a contract? If it is, it is nothing to the point that the valuation may have proceeded on the basis of error or that it constitutes a gross over or under value. Nor is it relevant that the valuer has taken into consideration matters which he should not have taken into account. The question is not whether there is an error in the discretionary judgment of the valuer. It is whether the valuation complies with the terms of the contract ."