Between Quoile quay and the castle, a channel has been cut in the river, creating a small island.

Quoile Pondage, County Down: Coots, not coal-boats, now ply the waters of what was once a marine estuary

There’s sward under my feet but behind me are mooring bollards and an imposing building that retains a warehouse’s rough-hewn edges. I lean against the nautical-looking railing where the River Quoile shoulders up to the wharf before sweeping and braiding through the pondage’s reed-fringed woodland. In the calm of early morning, with the river’s expansive meander, its willowed banks, and the crisp and shivering air that’s full of birdsong, Quoile quay’s remnants feel faintly dissonant.

I can hear wigeons’ zinging whistles but I can’t see them. I follow their voices down the wharf’s steep steps, into a sunlit fret of alder and ash backgrounded by a dense arras of head-high reeds. Not a chance of a sighting. At the insistence of tits and goldcrest, I move on.

Quoile quay: ‘I can hear wigeons’ zinging whistles but I can’t see them.’

A clearing exposes the wharf again, now a mossy, bramble-snagged wall; but what brings me up short are the flattened ribs of an old wooden coal-boat, heaving out of the earth like a newly excavated dinosaur fossil. This whole area might be soaked with the atmosphere of ancient fen and forest but the Hilda’scrumbling bones betray the back-story. This was formerly an estuary but since the Quoile barrier was built in the 1950s to control flooding from Strangford Lough, it has been completely transformed into freshwater habitat.

Flooding is still a constant. Heavy rain has brimmed river and culverts. The path is a causeway through shaded pools. I take a short detour to Quoile Castle, where a sign explains that the entrance to the 17th-century tower house is carefully orientated to keep feet “dry-shod”.

View from Steamboat quay, looking toward Strangford Lough.

At Riverrun jetty the surreal feeling returns. A throng of Game of Thrones fans are milling about taking selfies, oblivious to a lone goldeneye and the boreal glamour his wintering brings to the river’s pan. I hurry on to Steamboat quay. This was the last outpost of Downpatrick port, where ships from as far away as Liverpool disgorged. Now the only traffic is a flock of coots. Oh, not quite. My gaze is pulled skyward by a skein of noisy greylag following the Quoile’s final swagger before it slips, beyond my sight, into the lough’s saltwater.