Over the centuries the River Quoile has carried Vikings, steam ships and cargoes of coal and timber from as far afield as the Baltic and Canada. Today it's a river for leisure pursuits – popular with canoeists, anglers and wildlife enthusiasts.

Cadogan Enright is a councillor, environmental campaigner and chairman of the local canoe club. He takes Helen Mark out on the river to sing its praises, but also to point out concerns. He tells her that Downpatrick and the surrounding countryside were prone to tidal flooding in the past, but now the threat comes from the land - with increasing winter storms leaving the land saturated. Helen meets Robert Gardiner, chairman of the railway museum, who shows her how the water flooded their exhibition gallery last year and has threatened the museum's financial future.

Back on the riverbank, Helen meets Stephen O'Hare, a member of the River Quoile Trust which campaigns for improvements to the river. He shows her the remains of quays along the riverbank, which were once busy dockside areas for cross channel steam ships during the industrial revolution. Trade died out because of the unpredictability of the tides and the difficulties of navigating Strangford Lough out to the Irish sea, and came to a halt in 1957 when a flood barrier was built at the mouth of the river.

As for the Vikings – they haven't quite disappeared. Viking historian Philip Campbell and a group of enthusiasts have built a re-enactment village and a replica longship which they sail on stretches of the Quoile. He tells Helen that, as its dragon head noses through the waters which wind around the gentle drumlin countryside, he is filled with appreciation for the beauty of the river and its importance through the centuries.

Produced by Kathleen Carragher