Time and again in Africa, the promise of oil has brought conflict. But in nowhere more so than Sudan has competition over the resource played such a central role in blocking the road to peace. A civil war between Arab-led north Sudan and the country’s non-Muslim south has the dubious acclaim of being Africa’s longest: it raged from 1955-1972 and 1983-2005 as southerners fought for freedom from Khartoum’s repression.

A peace deal was signed three years ago by President Omar al-Bashir, the head of a hardline regime, and John Garang, who led the former rebels of the Sudan People’s Liberation Movement (SPLM) until he died in a helicopter crash seven months later. But the deal has unravelled in the past year – a move partly overlooked because of the international community’s focus on Darfur in western Sudan – and oil is part of the reason why. Most of Sudan’s reserves are in the south but the SPLM has been shut out of the sector. Production, which began in the late 1990s, has been controlled by Mr Bashir’s ruling National Congress party.