Unshaven, with the strap of his combat helmet dangling past his chin, Uche Nnabuihe, a Nigerian paratroop captain, wears the hollowed-out look of a soldier who has seen bad and expects worse.

Holed up in a remote creek in the Niger Delta, guarding an oil-rig belonging to Chevron, the US energy giant, he has ordered his platoon to fill sandbags to reinforce the two-storey houseboat the company provides.