Quest for the Holy Grail of Graig Trewyddfa, Swansea

Over about 200 years, up until the 1930s, the open valley of the River Tawe became one of the most heavily industrialised areas of the developed world. The ''Holy Grail'' which lay beneath the lands of Graig Trewyddfa, in Swansea, locally known as the ''Great Penvilia Five Foot Vein'', was renowned for its quality; smelting metals, at the time, required more than three parts of coal to every one o...