After the war, his interest in the Existentialist movement led to him corresponding with Simone de Beauvoir and visiting her in Paris. As well as his novels, Williams wrote both fiction and non-fiction for various journals. His autobiography, Clouds of Times and other stories, was published in 1989. He was lead consultant for a film about his uncle, Ellis Williams, which was broadcast on S4C in 2006. Williams was elected an Ovate (green robe) of the National Eisteddfod of Wales in Cardiff on 8 August 2008 for his substantial contribution to the field of literature in Wales.
Clouds of Time and Other Stories (Gwasg Carreg Gwalch, 1989) (Initially serialised in Welsh in Pais magazine and in English on BBC Radio 4, BBC Radio Wales and in The Countryman). "Clouds of Time" itself, first published in Welsh as "Cymylau Amser", is the life story of Williams's mother, Jane Rowland Jones, and how both she and her future husband sheltered a deserter from the trenches during World War I.