The languages belonging to the British subgroup of Celtic, i.e. Welsh, Cornish and Breton, have been the subject of thorough research for over a century now. Yet the phonological history of the prehistoric stages of these languages and the details of their connection with the other Celtic and Indo-European languages still present numerous unsolved issues. This volume aims to tackle the most acute problems of the historical phonology of British Celtic. Also it provides an up-to-date reference guide to British historical phonology in general, as well as a study of a large body of etymologies relevant to the correct evaluation of the historical phonology. This volume is of interest for the Celtologist, the Indo-Europeanist and the general historical linguist.