“[67]….It is enough to say….that in the context of VAT the final consumer who pays the tax has a sufficient economic connection with HMRC to be able to say that they have been enriched at his expense when the tax ought never to have been imposed on the services which were supplied….”
“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 … 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 … permit the latter to be re-opened. … Issue estoppel may arise where a particular issue forming a necessary ingredient in a cause of action has been litigated and decided and in subsequent proceedings between the same parties involving a different cuase of action to which the same issue is relevant one of the parties seeks to re-open that issue.”