Hurstpierpoint, West Sussex: Standing in a surprise bog, I spot water mint and pinch-plant, reminders of this vale’s marshy past

Between the village I live in, which is built along a low sandstone ridge, and where the land rises again to form the chalk scarp of the South Downs, there is a lowland vale. It is a damp region of rough grazing and ancient woods, of mist and shoe-stealing mud.

Often I cross it in a hurry, heading south to Wolstonbury Hill, a nearby summit giving views to Brighton and the Channel. Today I’ve barely left the village when I reach a splashy halt. As the slope relaxes into flatness, water pools around my boots. It appears a stream once oozed through this area, now pasture, and I’m standing in its former course. To either side of me an old streambed is visible, a waterlogged depression snaking through the grass.