Country diary: on the Severn Way with a heron and buzzard for company

Caersws, Powys Afon Hafren meanders to the flood plain, a broad, stately, river in comfortable middle age

Long before the Romans built their two forts at Caersws, the ridge to the west of the town was dominated by the ramparts of Cefn Carnedd. In the low afternoon sunshine the defensive banks that still rise above the hillside woodland were picked out by deep shadows.

The iron-age fortress stands above a kempt farmed landscape drained by the afon Hafren (river Severn) as it meanders across the valley floor. Only a few miles from where it rises, gathering volume from the tributary streams funnelling in from the many side valleys, it has already changed from a lively moorland torrent to a broad, stately, river in comfortable middle age.