The most reliable route to riches in Africa once lay via politics and “public” service. No surprise, since the state in many of sub-Saharan Africa’s 48 countries controlled the principal levers of the economy in the decades following independence.

Nigeria’s military rulers, with absolute powers over oil earnings, were among the best endowed. But the considerable fortunes they, and other politicians in resource-rich African countries, made were hidden in offshore accounts or behind webs of front companies and middlemen.