Hale L.J. said,

  1. This was a case management decision taken in the exercise of the judge’s discretion. This court will not intervene unless he has erred in principle or the result of his balancing exercise is plainly wrong.

  2. The overriding objective of the Civil Procedure Rules is to enable the court to deal with cases justly (rule 1.1(1)). But this includes, so far as practicable, saving expense, dealing with the case in ways which are proportionate to the amount of money involved, the importance of the case, the complexity of the issues and the financial position of each party, ensuring that the case is dealt with expeditiously and fairly, and allotting it an appropriate share of the court’s own resources (rule 1.1(2)).

  3. Controlling the issues and the evidence to be presented is an important part of that process. Expert evidence is to be restricted to that which is reasonably required to resolve the proceedings (rule 35.1). No party may call expert evidence without the court’s permission (rule 35.4(1)). The court may direct that evidence be given by a single joint expert instructed by the parties (rule 35.7) or appoint an assessor to assist the court (rule 35.15).

  4. Clearly, therefore, the court has to make a judgment on at least three matters:

(a) how cogent the proposed expert evidence will be;

(b) how helpful it will be in resolving any of the issues in the case; and

(c) how much it will cost and the relationship of that cost to the sums at stake.

Edited for ease of reading.