"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."
"This is the true basis of the doctrine and it ought only to be applied when the facts are such as to amount to an abuse: otherwise there is a danger of a party being shut out from bringing forward a genuine subject of litigation."
"In my opinion your Lordships should affirm it to be the law that there may an exception to issue estoppel in the special circumstance that there has become available to a party further material relevant to the correct determination of a point involved in the earlier proceedings, whether or not that point was specifically raised and decided, being material which could not by reasonable diligence have been adduced in those proceedings. One of the purposes of estoppel being to work justice between the parties, it is open to courts to recognise that in special circumstances inflexible application of it may have the opposite result, as was observed by Lord Upjohn in the passage which I have quoted above from his speech in the Carl Zeiss case [1967] 1 A.C. 853, 947."