British Thomson-Houston Co Ltd v Tungstalite Ltd In an action for damages for the infringement of letters patent, the plaintiffs made an application that, instead of directions under RSC Ord 53A, r 21A(2)(d) being given in the customary form, they should either deliver to the defendants a list of experiments on which they intended to rely upon the issue of infringement or else give notice that they did not intend to rely upon any such experiments