In the physical world, we say at tax-news, cherchez l'impot (tr: if something is strange in the real world, tax will explain it).

For instance, 18th century buildings in London often have blocked-up windows as a result of the notorious window tax. A new book to be published in January called The Great Hedge of India is the latest proof of the theory.

It's written by Roy Moxham, conservator of the University of London library, who became fascinated by the Great Hedge after chancing on a reference to it in the memoirs of a 19th century colonial administrator.

The East India Company, which ran the English half of India, imposed a salt tax which could cost a family 15-20% of its income; the other half of the country, run by Indian princes, had no salt tax. Result? The Great Hedge of India, built by the English, was constructed to stop smuggling of salt from the Indian to the English parts of the country.

The Great Hedge ran for 2,500 kilometres across India. This was no ordinary hedge: it was five metres high and four metres wide, made of prickly pear, thorny acacia and bamboo among other plants. Planted in the 1840s, the Great Hedge survived for fifty years, but eventually governmental and fiscal changes rendered it unnecessary and it was gradually broken down by cattle. Nowadays there is hardly a trace to be found of the Great Hedge of India.

Sic Transit Vectigali Mundum (tr: so pass the taxes of this world).