Iolo Williams tracks wildlife in one of Wales' extraordinary landscapes - the Cambrian Mountains. These hills are home to some of Wales’ best wildlife and Iolo’s task is to track it down – can he find Wales’ only golden eagle, or see an osprey actually catching a fish or capture a pine marten on camera? These remote uplands form the heart and spine of Wales. It's an area where the mighty rivers Rheidol, Ystwyth, Teifi, Tywi, Wye and Severn all have their sources; and is the least populated area of Wales. This is also Wales' lakeland as it has so many reservoirs including those in the Elan Valley. With a handful of roads crossing this stunning area of mid Wales, much of the landscape is only accessible on foot. It's a place where you can walk for miles without seeing a soul, but when you do find wildlife, it's always special. Iolo's first target is Wales' rarest and most elusive mammal, the pine marten, and he finds one at night lurking in a conifer forest. Iolo also looks for ospreys fishing on Llyn Clywedog. It's a magnificent bird of prey that's only relatively recently returned to nest in Wales after being extinct for centuries.