“In our view, a Tribunal, faced with an application for costs on the basis of unreasonable conduct where a party has withdrawn from an appeal should pose itself the following questions: - (1) What was the reason for the withdrawal of that party from the appeal? (2) Having regard to that reason, could that party have withdrawn at an earlier stage in the proceedings? (3) Was it unreasonable for that party not to have withdrawn at an earlier stage?” 26. The Upper Tribunal (Judge Berner and Judge Powell) in Market & Opinion Research International Ltd v HMRC[2015] UKUT 12 (TCC) (“ MORI ”) observed that: “15. The condition in rule 10(1)(b) is a threshold condition. It is only if the tribunal considers that a party has acted unreasonably in a relevant respect that the question of the exercise of a discretion can arise. 16. A determination of the question whether a party has, or has not, acted unreasonably is, accordingly, not the exercise of discretion, but a matter of a value judgment. An appeal against such a judgment, on a question of law, needs to e approached with appropriate caution. As Jacob LJ observed in Procter & Gamble UK v Revenue and Customs Commissioners[2009] STC 1990 , at [7], it is the FTT which is the primary maker of a value judgment based on primary facts. Unless the FTT has made a legal error, for example by reaching a perverse finding or failing to make a relevant finding or (misconstruing the statutory test) it is not for the appeal court or tribunal to interfere. Furthermore, as Lord Hoffman said in Biogen v Medeva[1997] RPC 1 , at p45: ‘Where the application of a legal standard such as negligence or obviousness involves no question of principle but is simply a matter of degree, an appellate court should be very cautious in differing from the judge’s evaluation’”