Once upon a time, Celtic languages were being spoken all over Europe from the British Islands till Anatolia, land of the Galatians (Greek name for the Celts), where Saint Paul addressed a letter to them. Today they eke out a marginal existence at the edges of Brittany, Wales, Scotland and Ireland. What are the features of these languages, their kinship and mutual intelligibility? Which policies eliminated them? How does the Celtic issue influence the Post-Brexit situation? Our colleague Diarmuid Johnson, who has written books on these topics, provides answers.