Tax lawyers have to apply the concepts contained in the tax legislation to facts created by taxpayers; this is not easy. In Barclays Mercantile Business Finance Ltd. v. Mawson (Inspector of Taxes) [2002] EWCA Civ 1853, [2003] S.T.C. 66, the Special Commissioners agreed with the Revenue; Park J. [2002] EWHC 1527 (Ch), [2002] S.T.C. 1068, agreed with the Special Commissioners but for rather deeper reasons. Now the Court of Appeal has accepted the taxpayer's characterisation, making some very critical remarks about both lower level decisions. Normally, that would be the end of the matter, but the members of the Court of Appeal went out of their way to say, as closely as judges can do, that the recent decision of the House of Lords in MacNiven v. Westmoreland Investments Ltd. [2001] 2 W.L.R. 377, the case which rewrote the still emerging rules about when composite transactions are treated as one single transaction for tax purposes, had left the courts with a test which is unworkable (e.g. para. [69]).