B racken and heather ripple across the plateau. I exhale into the chill autumn air and my breath mists a view that reaches all the way to Gower and the ochre peaks of Bannau Brycheiniog (formerly the Brecon Beacons). Far below, the Ogmore valley’s terrace houses look like tiny constellations but up here on Tarren y Fforch, it’s just me and a few sheep taking springy steps between tufts of bilberries. If this corner of the south Wales valleys feels a long way from its coal mining past, that is, partly, the point.

I’m hiking the new Llwybr Coedwig Cymru Trail , or Wales Forest Trail.…