Ten minutes walk from our house in rural Brittany, there is a lake, or étang, created by the neighbouring commune fifty years ago in the hope that it might become a tourist attraction.

The river that feeds the lake, with the improbably grand name Le Ruisseau de la Fontaine de Guervilly, used to mind its own business as it made its way towards a confluence with l’Hyére, a somewhat larger waterway that itself discharges into the Aulne, finally reaching the Atlantic a little south of Brest.