Arden LJ considered the principles to be applied when considering whether a party to civil litigation should be allowed to appeal a trial judge’s decision on the basis that a claim, which could have been brought before him but was not, would have succeeded if it had been so brought. She concluded: “CPR 52.8 provides that an appellant’s notice may not be amended without the permission of the court. When the court gives its permission, it must take into account the overriding objective in the CPR, which is to deal with cases justly. An application to amend a notice of appeal raises special considerations which do not apply to an application to amend a pleading prior to a trial. In the case of a pleading the court will (subject to any prejudice to the parties or to the administration of justice) readily give permission to amend so that the real dispute between the parties can be adjudicated upon. But on appeal the position is different. The simple fact is that there has already been a trial, and the significance of that is that the parties will have had an opportunity to put forward their cases, and incurred costs, and there will have been a decision. These points were powerfully put by May LJ in Jones v MBNA:
Civil trials are conducted on the basis that the court decides the factual and legal issues which the parties bring before the court. Normally each party should bring before the court the whole relevant case that he wishes to advance. He may choose to confine his claim or defence to some only of the theoretical ways in which the case might be put. If he does so, the court will decide the issues which are raised and normally will not decide issues which are not raised. Normally a party cannot raise in subsequent proceedings claims or issues which could and should have been raised in the first proceedings. Equally, a party cannot, in my judgment, normally seek to appeal a trial judge’s decision on the basis that a claim, which could have been brought before the trial judge, but was not, would have succeeded if it had been so brought. The justice of this as a general principle is, in my view, obvious. It is not merely a matter of efficiency, expediency and cost, but of substantial justice. Parties to litigation are entitled to know where they stand. The parties are entitled, and the court requires, to know what the issues are. Upon this depends a variety of decisions, including, by the parties, what evidence to call, how much effort and money it is appropriate to invest in the case, and generally how to conduct the case; and, by the court, what case management and administrative decisions and directions to make and give, and the substantive decisions in the case itself. Litigation should be resolved once and for all, and it is not, generally speaking, just if a party who successfully contested a case advanced on one basis should be expected to face on appeal, not a challenge to the original decision, but a new case advanced on a different basis. There may be exceptional cases in which the court would not apply the general principle which I have expressed. But in my view this is not such a case.’
The court must examine each application on its own facts in the light of the guidance to be found in the authorities. On that, the starting point is a passage from the speech of Lord Hershell in The Tasmania: ‘My Lords, I think that a point such as this, not taken at the trial, and presented for the first time in the Court of Appeal, ought to be most jealously scrutinised. The conduct of a cause at the trial is governed by, and the questions asked of the witnesses are directed to, the points then suggested. And it is obvious that no care is exercised in the elucidation of facts not material to them’.
It appears to me that under these circumstances a Court of Appeal ought only to decide in favour of an appellant on a ground there put forward for the first time, if it be satisfied beyond doubt, first, that it has before it all the facts bearing upon the new contention, as completely as would have been the case if the controversy had arisen at the trial; and next, that no satisfactory explanation could have been offered by those whose conduct is impugned if an opportunity for explanation had been afforded them when in the witness box.
Lord Hershell was there dealing with the situation where a party seeks to raise a new case by asserting that an accident happened in a different way from that which was suggested at trial. The passage stresses the importance of ensuring that the other party is not put at risk of prejudice. In his judgment in Jones v MBNA (a case under the CPR: see  of the judgment), Peter Gibson LJ helpfully elaborated the point, and expressed the view that it would be difficult to see how the court could ever, consistently with the overriding objective, allow a new point to be taken on appeal if further evidence might have been produced at trial on it or if the new point requires an evaluation by the appeal court of evidence which might be affected by seeing the witnesses.
38. It is not in dispute that to withdraw a concession or take a point not argued in the lower court requires the leave of this court. In general the court expects each party to advance his whole case at the trial. In the interests of fairness to the other party this court should be slow to allow new points, which were available to be taken at the trial but were not taken, to be advanced for the first time in this court. That consideration is the weightier if further evidence might have been adduced at the trial, had the point been taken then, or if the decision on the point requires an evaluation of all the evidence and could be affected by the impression which the trial judge receives from seeing and hearing the witnesses. Indeed it is hard to see how, if those circumstances obtained, this court, having regard to the overriding objective of dealing with cases justly, could allow that new point to be taken.
There is further useful guidance in this passage for the purposes of the present case. Peter Gibson LJ adopted the approach that, before allowing a new case to be raised on appeal, he had to be satisfied that, if the new case had been raised at trial, the other party would not have altered the way it conducted the case. Likewise, in this case, in my judgment the court has to be satisfied that SHS will not be at risk of prejudice if the new point is allowed because it might have adduced other evidence at trial, or otherwise conduct the case differently. It should consider for itself, as best it can, what factual issues are likely to be raised by the new case. Moreover, in circumstances such as the present, where there has been no disclosure relative to the new way in which the appellant seeks to put his case and virtually no opportunity to consider the matter, I do not consider that the court can reasonably expect the party against whom the amendment is sought to be made to be specific about the evidence he would have adduced had the point been raised earlier. If there is any area of doubt, the benefit of it must be given to the party against whom the amendment is sought. It is the party who should have raised the point at trial who should bare any risk of prejudice.
The circumstances in which a party may seek to raise a new point on appeal are no doubt many and various, and the court will no doubt have to consider each case individually. However, the principle that permission to raise a new point should not be given lightly is likely to apply in every case, save where there is a point of law which does not involve any further evidence and which involves little variation in the case which the party has already had to meet (see Pittalis v Grant  QB 605).”
Arden LJ, Dyson LJ
Commercial Agents (Council Directive) Regulations 1993 (SI 1993 No. 3053)
 EWCA Civ 978,
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