After studying anthropology at the London School of Economics, but not completing his degree, Gwyn began to travel extensively across Europe, living for long spells in Greece and Spain, working on fishing boats and as an agricultural labourer.

[2] Following a period of vagrancy and serious illness, he returned to Wales, where his experiences of travel catalysed his interest in writing, and he published three collections of poetry and prose poems.

His first work of fiction, The Colour of a Dog Running Away, set in Barcelona, received widespread critical acclaim and has been translated into many languages.

Tessa Hadley, in the London Review of Books described it as "an enthralling memoir of a young man going deeply and terribly astray."

Andrés Neuman, writing in Clarín (Argentina) called the book ‘Stunning… and as intimate and accurate as Virginia Woolf’s On Being Ill.[5] In recent years Gwyn has developed his career as a translator of poetry and short fiction by Latin American writers.