A Chancery judge has considered the weight to be given to expert evidence when only one party has called an expert in a given field. In Ashdown & Others v Griffin & Others [2017] EWHC 2601 (Ch), HHJ Matthews found that the court’s approach should be essentially the same as where an expert is instructed jointly by both parties: the expert’s evidence is likely to be accepted unless it is irrelevant, based on incorrect factual assumptions, or incredible.

In Ashdown, minority shareholders in an advertising company brought an unfair prejudice petition against the remaining shareholders. The company had been able to secure only a single account of any substance and had effectively ceased trading when that customer withdrew its advertising. The majority shareholders were connected with the customer, and one was on the boards of both companies. In an initial judgment on liability, a deputy judge found that he had unlawfully preferred the interests of the customer to those of the advertising company and ordered him to purchase the petitioners’ shares at a price to be determined in a subsequent hearing. After that hearing took place, but before the deputy judge could give his judgment, he unfortunately died, giving rise to the need for a rehearing on the quantum issues before a new judge. The petitioners encountered difficulties in meeting the costs of the rehearing and submitted only a single expert report, from a forensic accountant, whereas the respondents had reports from both an accountant and an advertising expert.

HHJ Matthews noted that the only authority before him as to how the court should approach evidence from a single expert was one in which the parties had instructed that expert jointly. In the present case, both parties had permission to call an advertising expert, but only one did so. However, the judge found that this placed the court in much the same position as if the expert had been instructed jointly. If the expert’s evidence was relevant, the court was obliged to take it into account and weigh it together with all the other evidence in reaching a conclusion. The likelihood was that the expert’s evidence would be accepted unless it was incredible or based on incorrect factual assumptions (a remote possibility in this case given that all relevant factual issues had been decided at the earlier liability hearing.) In this instance, the respondents’ advertising expert impressed the judge as being calm, knowledgeable and confident. The court accepted his assessment of the true value to the customer of the advertising it received. This contributed to a result in which the petitioners’ shareholding was valued at nil, compared to the petitioners’ own valuation of £205,000.


This case illustrates that when the court gives permission for expert evidence in a specific discipline, it is almost always advisable to take advantage of that permission. Not to do so will generally be to concede to the other party’s position on the issues of opinion covered by its expert, provided the expert is correctly instructed.