"It is appropriate to commence by noticing the distinction between cause of action estoppel and issue estoppel. Cause of action estoppel arises where the cause of action in the later proceedings is identical to that in the earlier proceedings, the latter having been between the same parties or their privies and having involved the same subject matter. In such a case the bar is absolute in relation to all points decided unless fraud or collusion is alleged, such as to justify setting aside the earlier judgment. The discovery of new factual matter which could not have been found out by reasonable diligence for use in the earlier proceedings does not, according to the law of England, permit the latter to be re-opened. .... The principles upon which cause of action estoppel is based are expressed in the maxims nemo debet bis vexari pro una et eadem causa and interest rei publicae ut finis sit litium. Cause of action estoppel extends also to points which might have been but were not raised and decided in the earlier proceedings for the purpose of establishing or negativing the existence of a cause of action. In Henderson v Henderson (1843) 3 Hare 100 , 114-115, Sir James Wigram V-C, expressed the matter thus:
'In trying this question, I believe I state the rule of the court correctly, when I say, that where a given matter becomes the subject of litigation in, and of adjudication by, a court of competent jurisdiction, the court requires the parties to that litigation to bring forward their whole case, and will not (except under special circumstances) permit the same parties to open the same subject of litigation in respect of matter which might have been brought forward as part of the subject in contest, but which was not brought forward, only because they have, from negligence, inadvertence, or even accident, omitted part of their case. The plea of res judicata applies, except in special cases, not only to points upon which the court was actually required by the parties to form an opinion and pronounce a judgment, but to every point which properly belonged to the subject of litigation, and which the parties, exercising reasonable diligence, might have brought forward at the time.'
"a) As the Federal Patent Court rightly stated, the examination of patentability must take into account the entire existing state of the art without restrictions, ie, including the cited prior art which ... was already the subject matter of the examination in opposition proceedings and in opposition appeal proceedings before the European Patent Office. The fact that the nullity proceedings must take account of the entire matter at issue is a necessary consequence of the function of these proceedings and its relationship to the objection proceedings. It is true that the decisions resulting from such proceedings represent expert opinions of considerable importance that must be considered as part of the finding of facts and the evaluation of the evidence; they cannot, however, enjoy any further legal effect (cf., although diverging in part, Brinkhof , l993 GRUR l77, l83, and the references cited by the Federal Patent Court).
".... It seems to me reasonable to infer ... that the intention behind the relevant provisions of the European Patent Convention is that revocation of a European patent should primarily be a matter for the national court of the designated state and that when validity is put in issue in proceedings for infringement of a European patent, which can only be brought in the appropriate court of the disputed state, the intention is that both infringement and validity should be litigated in that court."
"It is obvious, therefore, that the mere fact that the judgment puts an end to and finally settles the controversy which arose in the particular proceedings, is not of itself sufficient to make it a final and conclusive judgment upon which an action may be maintained in the Courts of this country ...."