We are at the Stori Brymbo heritage site, which was an iron mine and smelting plant until 1990. Outside it is cool, stormy and wet, but we’re sheltered under a galvanised roof with the wind rattling and the rain tapping. Beneath us, a sandy, crumbling layer of rock formed 300m years ago from a great thickness of mud and silt that settled in a vast river delta system that once covered this part of Wales.
If I squint my eyes, I imagine the vast, stifling, steaming jungle; no grass or flowers, just tall trunks towering above and ferns below, insects flying all around. This was the Carboniferous era in the tropics, long before any dinosaurs or other land animals, and the first “trees” – club mosses, giant horsetails – grew by 10 to 30 metres in a few months, before dying and falling into the swamps to eventually form our coal.
