
Iolo Williams explores four of Wales's longest river valleys from sea to source.

Iolo Williams explores the Usk valley, from Newport’s urban wildlife to ground-nesting birds, a huge lesser horseshoe bat roost and scarce firecrests.

Iolo Williams explores the Tywi river valley, from Llansteffan’s coastal dunes to fallow deer ruts, ancient oak woodlands, and the remote heights of the Tywi Forest.