All Things Betray Thee, by Gwyn Thomas, is a novel of early industrialism in South Wales.

It is both a personal story and an account of the origin of the industrialised and mostly English-speaking society of the South Wales Valleys.

Set in the new town of Moonlea, a fictionalised version of Merthyr Tydfil, it is told from the viewpoint of a travelling harpist, Alan Hugh Leigh, who is looking for his friend, the singer John Simon Adams.

But his friend has become a populist leader among the ironworkers, who are involved in a bitter industrial conflict.

[4] All Things Betray Thee was adapted as a three-part radio drama by Alan Plater and directed by Alison Hindell, with Ian Hughes as Alan Hugh Leigh and Patrick Brennan as John Simon Adams.