January, 1890 Britain threatens Portugal with an Ultimatum: Abandon south-east Africa or face a naval bombardment of Lisbon. Three centuries earlier, the poet Luis de Camoes described the region at issue - Behold the lake which is the Nile's source. And the green Zambezi, too, begins its course. Further upstream, the river becomes serpentine, twisting itself into a vast swamp, known to Europeans as Elephant Marsh, choked with papyrus, monstrous baobabs, and marabou storks like coffins. Every mud bank has a gang of crocodiles, the air thick with mosquitoes and the nearest horizon a tousled fringe of swamp palms ... could the European Powers go to War over such a Wilderness?