“…But Dr Frame's words apply equally to the inherent fictions of tax law. He says: 54 I should note here two dangers of the fiction as a device for preventing the exploitation of legal forms to frustrate the intent of legal policy. First, use of the device strengthens the legitimacy and likely success of such exploitation in respect of those legal forms [that] are not specifically targeted -thus, if legal facts A, B, and C are specifically treated as if they were legal fact T (Taxable), then by implication legal fact X, which has not been designated, is not to be so treated, however artificial its existence may appear to be.…”