Gwyn Thomas was born in Cymmer, Porth in the Rhondda Valley, the youngest of 12 children to coalminer Walter Morgan Thomas and his wife. His mother died when he was aged six, and he was resultantly brought up by his sister, often with handouts from the local soup kitchen.
After winning a scholarship, Thomas studied Spanish at the University of Oxford. Plagued by mysterious health problems, terribly poor and depressed, it was only after spending a summer and a term at the end of his second year at Complutense University of Madrid, thanks to a miners' scholarship, that he decided to complete his studies. Thomas was diagnosed at the age of 23 with an undiagnosed thyroid malfunction that had been poisoning him for years, which was operated on to avoid his death.
On graduation and wanting to be a writer, Thomas struggled to establish himself during the 1930s depression. He took on part-time lecturing jobs across England, while trying to get his novel Sorrow For Thy Sons published.
He married his childhood friend Lynn Williams in Pontypridd Registry Office on 5 January, 1938. Failing to pass the British Army medical at the outbreak of World War Two thanks to 20years of smoking, he returned to Wales in 1940 and taught at the WEA. He then became a schoolteacher, first teaching French in Cardigan, and then Spanish in Barry at Barry County Boys School for 20 years.
Post war, his wife decided to send some of his short stories to three publishers, who all accepted the scripts for publication. Approached in 1951 by a BBC Radio Wales producer to write for the radio, he returned to his childhood memories of 1920s South Wales to create Gazuka!
A prolific novelist and short-story writer, he became a regular on chat shows shut as the Brain's Trust, and after 20 years of teaching in 1962 he became a full-time writer and broadcaster, retiring with his wife to Peterstone.
However, due to a combination of diabetes, heavy drinking and smoking, his health began to fail in the late 1960s. In 1981 Thomas collapsed and was taken to the University Hospital of Wales in Cardiff, where he died on 13 April, shortly before his 68th birthday.
In 1993, Sir Anthony Hopkins portrayed Thomas in a BBC Wales television production of his memoir Selected Exits.Thomas was commemorated at an event in Barry Memorial Hall on Saturday 21 November 2009, when Pride In Barry announced it was placing a Blue Plaque on the Old College Inn, Barry, where his old school classrooms used to be.