I recently discovered that I am entitled to an occasional tax-free breakfast, because I cycle to work. (The UK government advises that “Under general principles such meals are a taxable benefit in kind but regulations exempt them from tax, as long as they are provided on designated ‘cycle to work’ days.’’) Good to know – and a reminder that the idea of using the tax system to promote environmental goals has taken a wrong turn somewhere.

The basic idea behind green taxes is sound. Since people usually respond to financial incentives, whenever something is taxed they tend to do less of it. Usually, that is a problem. When the government taxes income, we slack off. When the government taxes moving house, we may stay in the wrong size house on the opposite side of town from our new job. What’s more, whenever the tax dissuades someone from earning income or moving house, the tax office loses out as well.