A great bulging, seeping mass of black vapour was passing over the river valley, this cumulonimbus was shedding some excess weight upon the already flooded fields below. It soon cleared though, leaving the land dripping and running with fresh precipitation. The sky was revealed from behind the storm; it glowed a suffuse, delicate blue – the shade of blue that only appears just before sunset begins. The pale sun was dropping gradually below the dark crest of the South Downs, while just left of it another solid lump of storm cloud was rising from over the unseen channel – it was miles distant, creeping along behind the hills like a hulking creature.

I followed a footpath down to the level of the floodplain, its course took me right along the edge of a great flooded field – known as the north brooks; essentially a winter spill-over area for the river Arun to unload its excesses. This shallow, grassy lake had attracted vast numbers of wildfowl; thousands of Wigeon and Teal gathered on the smooth surface of the waters. Distant swans shone white against the darkening land, a group of stately pintail scuttered across the water and bulky Shoveler cruised stealthily through the sedges.

I stopped suddenly on the path, realising properly the spectacle before me, I stood there gasping at the living tapestry of sight and sound. The sky was exquisitely coloured; where the suns dying light touched the frothy layers of high clouds they reflected shades of fresh mango or paler lemon sorbet. The distant cumulonimbus brooded in silhouette, but sported a gilded edge of saffron light around its towering peaks. The sun cast its shadow far onto the ragged undersides of the other clouds, setting off the burning colours with dashes of smoky grey. As the sunlight grew more distant so the blue of the sky behind the clouds faded to watery yellow – and all this atmospheric drama was perfectly reflected in the crystal floodwaters that spread out in front of me. A few synchronised flocks of starlings fluttered over the plains to join a larger pre-roost murmuration somewhere – forming into throbbing spheres as they danced across the sky together.

Standing sculpture-like from the meadows were the wintry forms of twisted oaks and slender willows, tufts of rushes and reeds framed the field edges and the underwater ditches, while lonely gates and fence posts marked where paths and boundaries once existed – until nature took over. Adding to the whole experience was the ceaseless whistling and gabbling of all the shoals of duck that were spread over the landscape – a pleasantly wild, evocative sound that was both thrilling and relaxing. As the sky deepened in redness a bow-winged heron, purposeful and silent, drifted across it on the way to roost.

It then occurred to me that this vision, in this place, has probably been unchanged for thousands of years (excepting different weather); the birds migrate here every winter, the fields of the valley flood every winter, the downs have been here millennia, the sun drops on the same axis every winter. If I had travelled four thousand years back in time on that evening, in the same place, the awe-inspiringly wild and dramatic sight of all those birds and all that water and all that sky – would almost certainly be the same as it is now. It was a moment that transcended time but was firmly rooted in place. The gorgeous natural artwork I had witnessed, painted by God himself, vanished as the light failed, I left feeling rapturously euphoric – this is what nature does to me, it is why I need it, as a drug, an antidote to the modern world.