Usk

Iolo Williams explores four of Wales's longest and most varied river valleys from sea to source, uncovering their hidden wonders and remarkable wildlife, including a few special species.

In the first episode, Iolo journeys through South Wales to explore the River Usk. His 77-mile journey begins near the industrial docklands of Newport, where the iconic transporter bridge stands as a gateway to surprising urban biodiversity. In what many would 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 to the gravelly stretches near Usk town, the river becomes a vital spawning ground for rare shad, a sea fish that migrates to freshwater to lay its eggs. On the quiet shingle banks, Iolo uses his specialist licence to monitor the incredibly well-camouflaged nests of little ringed plovers, watching as the birds carefully navigate back to their clutches.

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

The journey takes a historical turn at Llanfoist, where Iolo visits the Monmouthshire and Brecon canal. Deep within a dark, damp tunnel beneath the 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.

Above the valley floor, Iolo heads to the dramatic limestone cliffs of Craig y Ciliau, an old quarry that is now a national nature reserve. Here, among rare Arctic-alpine plants like mossy saxifrage, Iolo observes the wheatear nesting in the scree and witnesses an unusual sight - redstarts, typically woodland glade nesters, raising their young in holes in the ground.

As evening falls near Brecon, 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, observing their unique light sampling behaviour before they head out to hunt.

The adventure nears its end in the coniferous woodlands above the valley floor near Sennybridge, where Iolo strikes gold by witnessing a territorial dispute between two tiny firecrests, displaying their orange crests flaring like torches. The journey concludes at the remote Usk reservoir, nestled in the shadow of the Black Mountain peaks, where mating six-spot burnet moths provide a final splash of colour to an epic exploration of one of Wales's most varied river systems.