The largest digging machine ever built lies twisted and wrecked by a missile strike in the wild heart of Africa. The waterway it began to cut was never finished, but decades later is flowing now with the floodwaters from a heating planet. Camped out along it are tens of thousands of people, destitute, starving, clinging on. Is this the end of the past, or the beginning of the future? This is the Sudd, South Sudan.