Gandhi's salt march is well known, but I had no idea of the background: the fact that throughout a large part of the period of British rule in India there was a very heavy tax on salt, which was enforced by the creation of a "Customs Line" 2500 miles long to prevent smuggling, mostly consisting of a thick hedge, guarded by customs officials.

I came across the book The Great Hedge of India by Roy Moxham in a remainder shop near the office the other day.

He describes how he became interested in the history of the salt tax and particularly the hedge after he came across a mention of it in an old book about India.

He spent a lot of time researching the hedge, both in old books and maps and also on the ground. It's a fascinating story, and although most of the hedge has disappeared, he found parts of it. His description of his travels in search of the hedge and of his growing obsession with the subject and its history is very entertainingly written.

He estimates that a 19th Century peasant in India actually needed to spend the equivalent of about two months of his income to provide enough salt for his family for the year (an interesting statistic for anyone tempted to think the British Empire in India was benign). The resulting salt deficiency among the people was seriously damaging to health and made people much more susceptible to the effects of famine.

From the book:

I was deeply shocked by what I discovered about salt. When I had the idea of finding the remnants of the Customs Hedge, I had imagined the barrier as a piece of British whimsy constructed to collect a minor tax. I had assumed it was merely a flamboyant boundary, perhaps fashioned by administrators with fond memories of English hedgerows. It was a terrible discovery to find that it had been constructed, and ruthlessly policed, so as to cut off an affordable supply of an absolute necessity of life.