(Court of Appeal; Thorpe, Wall and Elias LJJ; 25 June 2009)
The parties negotiated an agreement, which was eventually approved by the court in the form of a consent order. Subsequently the husband sold his company shares for a great deal more than the estimated value of the shares disclosed in the course of the negotiations. The wife applied for leave to appeal and/or to set aside the consent order on the basis that the sale represented a new event, or that there had been material non-disclosure. The judge granted the wife permission to appeal on the basis that the wife had established an unforeseen and unforeseeable supervening event, within the principles set out in Barder v Caluori  2 All ER 440. The husband appealed.
Mistake as to value did not fall within the Barder principles. The court had first to consider whether the agreement or consent order had been vitiated by one of the classic principles, such as misrepresentation, breach of duty of full, frank and clear disclosure, fraud or undue influence. If there was no vitiating element, the judge should proceed to rule on whether there had been a Barder event. In this case Barder did not apply; there had been no mistaken premise, because there had, on the evidence, been no consensus as to the value of the husband's shares. There had been no dramatic and unexpected turnaround in the company's performance, nor could it be said that the sale of the shares had been either unforeseen or unforeseeable.