A new oil frontier is opening on Africa’s western coastline, which is now producing around 5m barrels of oil per day, rising fast. Last year oil exports were worth over $110 bn - nearly four times the OECD countries’ total aid to sub-Saharan Africa.

Yet the producer countries’ citizens are typically poorer and more badly governed than their African peers. Despite $400 bn in oil earnings since 1970, Nigeria’s income per capita is 25 per cent lower than the sub-Saharan African average. Angola’s $31bn budget this year is roughly equivalent to all OECD countries’ aid to sub-Saharan Africa, yet it suffers the world’s second worst mortality for children under five, according to the UN. Equatorial Guinea’s infant mortality has risen sharply since it found oil. And so on.