22 September 2013 we enjoyed a splendid day walking up the Cat’s Back (Crib y Garth), Black Mountains, on the western edge of Brecon Beacons National Park. This spectacular ridge (arête) created in the Ice Age rises 240 metres from the parking below. Duncan Hawley’s usual ceaseless flow of information and careful tutoring revealed the evidence of the vast plains and meandering rivers of the early semi-arid Devonian period and drew us into discussion of several phenomena on which consensus has not yet been reached.