 She is particularly well known for her studies of early Welsh and Breton history.She is co-director, with Prof. James Graham-Campbell, of the interdisciplinary 'Celtic Inscribed Stones Project', established to build a database of all known early medieval Celtic inscribed stones.For the last twenty years she has also convened a major research group, known as the 'Bucknell Group', with the aim of examining the social significance of early medieval European charters.