 The coal mining industry of the Rhondda was artificially buoyed throughout the war years , though there were expectations of a return to the pre @-@ 1939 industrial collapse after the end of the Second World War . There was a sense of salvation when the government announced the nationalisation of the British Coalmines in 1947 ; but the following decades saw a continual reduction in the output from the Rhondda mines . From 15 @,@ 000 miners in 1947 , Rhondda had just a single pit within the valleys producing coal in 1984 , located at Maerdy . The decline in the mining of coal after World War II was a country wide issue , but South Wales and Rhondda were affected to a higher degree than other areas of Britain . Oil had superseded coal as the fuel of choice in many industries and there was political pressure influencing the supply of oil . Of the few industries that were still reliant on coal , the demand was for quality coals , especially coking coal which was required by the steel industry . Fifty percent of Glamorgan coal was now supplied to steelworks , with the second biggest market being domestic heating , which the ' smokeless ' coal of the Rhondda became once again fashionable after the publication of the Clean Air Act . These two markets now controlled the fate of the mines in the Rhondda , and as demand fell from both sectors the knock @-@ on effect on the mining industry was further contraction . In addition exports to other areas of Europe , traditionally France , Italy and the Low Countries , experienced a massive decline ; from 33 per cent around the start of the 20th century to roughly 5 per cent by 1980 . 
