When Nomatter Tagarira, a spirit medium, claimed that she could conjure refined diesel out of a rock by striking it with her staff, ministers in Robert Mugabe’s Government believed that they might have found the solution to Zimbabwe’s perennial fuel shortage. After witnessing her apparently miraculous gift they gave her five billion Zimbabwean dollars in cash (worth £1.7 million at the start of the year but now worth one seven-hundredth of that) in return for the fuel. Ms Tagarira was also given a farm, said to have been seized from its white owner during Mr Mugabe’s lawless land grab,...