When Napoleon was finally imprisoned on St. Helena, the British government thought it prudent to occupy a small volcanic island named Tristan da Cunha, which was located about twenty degrees south of St. Helena.  It was assumed that, if the wily French emperor attempted an escape from his island lodgings, Tristan da Cunha would present an ideal staging area. Occupation of Tristan would forestall such an eventuality.  Within a few years a fort and barracks had been constructed, and the island was eventually garrisoned; a few dairy cows completed the island’s fortification.