Plot: Levison Wood continues his epic 650-mile journey on foot, following the annual migration of Botswana's 130,000 elephants, and faces his toughest challenge yet. Together with his guide Kane, Lev treks along the route taken by the male elephants through the immense salt pans of the Makgadikgadi, via the frontier town of Gweta, to the edge of the Okavango Delta