Oliver Balch finds out about oil exploration, foreign investment and tax imbalances in Africa’s newest petro-state

The phrase "striking oil" carries two dictionary definitions: the formal, to "discover petroleum while digging for it"; and the informal, "to become very rich or successful". In real life, the two aren’t always as neatly tallied.

The story of West Africa’s oil rush over the past half-century or so painfully illustrates the mixed fortunes that so-called black gold can bring. Nowhere is its tarred hand more in evidence than Nigeria, the continent’s largest crude oil exporter.