IRC v. Garvin, [1981] 1 WLR 793, [1981] UKHL TC, 55 T.C. 24 (HL)

In obiter dicta, Lord Russell of Killowen "venture[d] to doubt the ability of the Crown ... having levied a tax on the basis that the transaction was a dealing in capital, then to assert that it can indirectly, by counteraction be treated as giving rise to taxable income."

Regarding there having been a concession by the Inland Revenue that the receipt before the Court should not be taxed twice, Lord Bridge stated (at pp. 90-91 (TC)):

I agree with others of your Lordships who have expressed the view that it would be most unsatisfactory that the avoidance of such double taxation should be dependent on a concession. If any doubt on the point is removed by statute, so much the better. But if an attempt were made to levy both taxes in respect of a single receipt—a contingency which I can, I hope, be regarded as remote—I can see a powerful argument being mounted to the effect that, if a receipt falls to be treated as income and taxed as such under one code, it must, by necessary implication, be exempt from liability to taxation as a capital receipt under another code.