Each winter, alone in the pitiless ice deserts of Antarctica, deep in the most inhospitable terrain on Earth, a truly remarkable journey takes place as it has done for millennia. Emperor penguins in their thousands abandon the deep blue security of their ocean home and clamber onto the frozen ice to begin their long journey into a region so bleak, so extreme, it supports no other wildlife at this time of the year. In single file, the penguins march...