Iolo Williams returns to explore Wales’ river valleys in second series

Iolo Williams will explore four of Wales’ longest and varied river valleys from sea to source, uncovering their hidden wonders and remarkable wildlife, in the second series of Iolo’s River Valleys.

In the first episode, which will air on BBC One Wales on Wednesday 6 May, Iolo journeys through south Wales to explore the river Usk.

In what some might consider abandoned wasteland, Iolo discovers a pollinator’s paradise filled with different flowering plants, home to red admiral and speckled wood butterflies, as well as the remarkably named javelin wasp, a parasite with a long ovipositor that looks like a sting.

Moving upstream, the river becomes a vital spawning ground for rare shad, a sea fish that migrates to freshwater to lay their eggs.

On the quiet shingle banks, Iolo uses his specialist licence to monitor the incredibly well-camouflaged nests of little-ringed plovers.

The river’s health is further evidenced by its abundant insect life, where Iolo finds various species of mayflies, which provide a feast for the local brown trout population.

Deep within a dark, damp tunnel beneath the Monmouthshire and Brecon Canal, Iolo searches for the European cave spider.

He reveals the fascinating life cycle of these light-shunning arachnids, from their “cotton wool” egg sacs to the spiderlings that use silk parachutes to find new homes.

Iolo then heads to the dramatic limestone cliffs of Craig y Ciliau. Here, he observes the wheatear birds nesting in the scree and witnesses an unusual sight; a redstart, typically woodland glade nesters, raising their young in holes in the ground.

As evening falls near Bannau Brycheiniog, Iolo joins the Vincent Wildlife Trust to witness the emergence of one of Britain’s rarest mammals: the lesser horseshoe bat.

Using thermal and infrared technology, he gets a rare insight into a massive maternity roost of 500 adults.

The adventure nears its end in the coniferous woodlands above the valley floor near Sennybridge, where Iolo hits “gold dust” by witnessing a territorial dispute between two tiny firecrest birds.

The journey concludes at the remote Usk Reservoir, where mating six-spot burnet moths provide a final splash of colour to the exploration of one of Wales’ most varied river systems.

The first episode of Iolo’s River Valleys’ second series will air at 7pm on BBC One Wales, and will be available to watch on iPlayer.