“It is undisputed that our jurisdiction is supervisory only. That is, if we are to allow the appeal we must be satisfied that the decision was one at which the Commissioners could not reasonably have arrived. That understanding of the law derives from the judgments of Farquharson J in Mr Wishmore Limited v Customs and Excise Commissioners[1988] STC 723 , of Dyson J in Customs and Excise Commissioners v Peachtree Enterprises Ltd[1994] STC 747 and of the Court of Appeal in John Dee Limited v Customs and Excise Commissioners[1995] STC 941 . The cases show that we must limit ourselves to a consideration of the facts and matters which were known when the disputed decision was made, so cannot take account of developments since that time, and that we may not exercise a fresh discretion. In other words, if the decision was flawed we must allow the appeal and leave HMRC to make a further determination if they so choose. If we are persuaded the decision was flawed but that, had HMRC approached the matter correctly, they would inevitably have arrived at the same conclusion we should dismiss the appeal.”
“… the Commissioners will not arrive reasonably at a decision if they take into account irrelevant matters, or fail to take into account all relevant matters.”