"Publicity is the very soul of justice. It is the keenest spur to exertion, and the surest of all guards against improbity. It keeps the judge himself, while trying, under trial."
However, the discretion is there and an example of its exercise is provided by Mr Justice Kitchin's judgment in Prince of Wales v Associated Newspapers Ltd.  EWHC 11 (Ch) (13 Jan 2006). This is a claim in which HRH is suing the publisher of the Mail of Sunday for breach of confidence and copyright infringement in respect of a journal that he kept of the visit that he made to Hong Kong at about the time of the handover to the Peoples' Republic found their way into the hands of the defendant publisher.
The judge decided to make an order under this rule for the following reasons:
(1) The documents in issue were closely related to the very subject matter which the prince was seeking to protect by means of this action and which were at least arguably confidential.
(2) The order is to last only until the disposal of Prince Charles's summary judgment application which is due to come on within a month or so.
(3) The order should make it easier to hold the trial in public.
It will be interesting to see how often this case is referred to in future.