“The court should not make an order against a practitioner precluded by legal professional privilege from advancing his full answer to the complaint made against him without satisfying itself that it is in all the circumstances fair to do so. This reflects the old rule, applicable in civil and criminal proceedings alike, that a party should not be condemned without an adequate opportunity to be heard. Even if the court were able properly to be sure that the practitioner could have no answer to the substantive complaint, it could not fairly make an order unless satisfied that nothing could be said to influence the exercise of its discretion. Only exceptionally could these exacting conditions be satisfied. Where a wasted costs order is sought against a practitioner precluded by legal professional privilege from giving his full answer to the application, the court should not make an order unless, proceeding with extreme care, it is (a) satisfied that there is nothing the practitioner could say, if unconstrained, to resist the order and (b) that it is in all the circumstances fair to make the order.”