Patrick Sims-Williams is Professor of Celtic Studies at the University of Wales, Aberystwyth. He is the author of '"Religion and Literature in Western England, 600-800'" (1990) and "'Britain and Early Christian Europe'" (1995). He is also the co-editor of "'Ptolemy: Towards a Linguistic Atlas of the Earliest Celtic Place-Names of Europe'" (2000), and the editor of "Cambrian Medieval Celtic Studies,"