Iolo Williams explores four of Wales's longest river valleys from sea to source.
Episode 1
Usk
May 6, 2026
Iolo Williams explores the Usk valley, from Newport’s urban wildlife to ground-nesting birds, a huge lesser horseshoe bat roost and scarce firecrests.
Episode 2
Tywi
May 13, 2026
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.
Episode 3
Teifi
May 20, 2026
Iolo explores the Teifi river valley, and finds a slow worm hunting, meets a coracle fisherman, is thrilled by a fishing Otter, and watches a pair of kestrels at their nest.
Episode 4
Dee
May 27, 2026
Iolo explores the stunning Dee valley, from wintering birds along the estuary, to displaying black grouse on moorland, rare freshwater-pearl mussels, and spawning sea trout.