The Senior Courts Costs Office Guide 2013 correctly describes the approach to disclosure in detailed assessment hearings of potentially privileged documents:
“If, having examined documents lodged with or produced to the court, the court is minded to determine a point of dispute wholly or partly in favour of the receiving party it does not automatically follow that the paying party will have a right to see all of the documents relied on by the court in reaching that decision. The court should enquire of the paying party whether the paying party is content to accept that ruling (subject to appeal) or whether the paying party wishes to see the documents relied on by the court in making the ruling. In many cases the paying party will be content to agree that the court alone should see those documents. The alternatives (see below) may lead to additional delay and an increase in costs.
(b) If the paying party declines to accept the court’s ruling without inspecting documents, then, save as explained in paras (f) to (h) below, the court will put the receiving party to his election between showing the documents in question to the paying party or not relying upon them and offering to prove the fact of which the document is evidence by some other means. Alternatively the receiving party may decide to withdraw the claim for the costs of it. The court may give directions enabling the receiving party to have a fair opportunity to provide other evidence. In reaching its final decision on the issue the court will not take account of documents which the receiving party has elected not to show to the paying party.”
Those costs draftsmen and costs lawyers who continue to believe that they can simply show the documents they rely on to the judge without also having to potentially show the same to the other side have misunderstood the true position.