When the historian Peter Burke wrote in 1987 ‘It is high time for a social history of language’, he could scarcely have imagined that the first to meet the challenge would be the Welsh. In November 2000 the University of Wales Centre for Advanced Welsh and Celtic Studies, a research institute which specializes in long-term collaborative projects on the history, language and literature of Wales and the other Celtic countries, completed in eleven volumes the first scholarly enterprise devoted to the social history of the Welsh language.