A veteran nature writer walks the length of Britain in pursuit of spring, and of hopeFed up with bleak headlines of biodiversity loss, acclaimed nature writer Roger Morgan-Grenville sets out on a 1,000-mile walk through a British spring to see whether there are reasons to be hopeful about the natural world. His aim is to match the pace at which the oak leaves emerge, roughly 20 miles north each day. Fighting illness, blizzards and his own ageing body, he visits every main habitat between Lymin