This week Mrs Ngozi Okonjo-Iweala is back. Who, you might say? She is the person, in the early 2000s, who as finance minister under Nigeria’s democratically elected president, Olusegun Obasanjo, turned the Nigerian economy around 180 degrees. Before that, under the military dictatorship which had ruled Nigeria, Africa’s most populated country, for 18 years, economic growth, despite the huge oil wealth, had not risen above 3% a year. The economy was badly sick and billions of dollars were skimmed off by the dictator, Sani Abacha, and those around him. Inflation and bank indiscipline brought havoc and instability to the economy. The poor got poorer. With success under her belt she departed Nigeria to be a vice president of the World Bank. Now the new president, an Obasanjo protégé, Goodluck Jonathan, has brought her back, presumably to engineer another surge. On her last watch she killed inflation, paid off Nigeria’s huge...