“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.”
“The Court has an inherent power, which any Court of Justice must possess, to prevent misuse of its procedure in a way which although not inconsistent with the literal application of its procedural rules, would nevertheless be manifestly unfair to a party in litigation before it or would otherwise bring the administration of justice into disrepute among right-thinking people. The circumstances in which abuse of process can arise are very varied; those which give rise to the instant appeal must surely be unique. It would, in my view, be most unwise if this House were to use this occasion to say anything that might be taken as limiting to fixed categories the kinds of circumstances in which the Court has a duty, (I disavow the word discretion) to exercise this salutary power.”
“But Henderson v Henderson abuse of process, as now understood, although separate and distinct from cause of action estoppel and issue estoppel, has much in common with them. The underlying public interest is the same; that there should be finality in litigation and that a party should not be twice vexed in the same matter. This public interest is reinforced by the current emphasis on efficiency and economy in the conduct of litigation, in the interests of the parties and the public as a whole. The bringing of a claim or the raising of a defence in later proceedings may, without more, amount to abuse if the court is satisfied (the onus being on the party alleging abuse) that the claim or defence should have been raised in the earlier proceedings if it was to be raised at all. I would not accept that it is necessary, before abuse may be found, to identify any additional element such as a collateral attack on a previous decision or some dishonesty, but where those elements are present the later proceedings will be much more obviously abusive, and there will rarely be a finding of abuse unless the later proceeding involves what the court regards as unjust harassment of a party. It is, however, wrong to hold that because a matter could have been raised in earlier proceedings it should have been, so as to render the raising of it in later proceedings necessarily abusive. That is to adopt too dogmatic an approach to what should in my opinion be a broad, merits-based judgment which takes account of the public and private interests involved and also takes account of all the facts of the case, focusing attention on the crucial question whether, in all the circumstances, a party is misusing or abusing the process of the court by seeking to raise before it the issue which could have been raised before. As one cannot comprehensively list all possible forms of abuse so one cannot formulate any hard and fast rule to determine whether, on given facts, abuse is to be found or not.”
“The fact that the CAB was not a party as such to those proceedings does not in my view alter the position. It seems to me that the public interest in ensuring finality requires that the decision of the Tribunal is respected and should be treated as the determination of the issue of authority. …I think that this new claim is an abuse of process and ought to be struck out.”
“If the parties to the later civil proceedings were not parties to or privies of those who were parties to the earlier proceedings then it will only be an abuse of the process of the court to challenge the factual findings and conclusions of the judge or jury in the earlier action if (i) it would be manifestly unfair to a party to the later proceedings that the same issues should be relitigated or (ii) to permit such litigation would bring the administration of justice into disrepute.”