Tonight, like every other night for weeks, convoys of trucks will set out across the southern Libyan desert and head towards the border with Sudan, 250 miles away. They will drive from dusk with lights dimmed in a bid to avoid detection. This is a clandestine operation – though hardly secret. Once across the frontier, the convoys will divide, some travelling south, others setting out to the east. Most reporting from Sudan has so far focused on the street battles in the capital, the 500 or more dead and 4,000 wounded, the impending humanitarian crisis and the evacuation of foreign...