I specialise in historical linguistics and in theoretical and dialect syntax, working primarily on material from Celtic, Slavonic and Old/Middle English. I am interested in the mechanisms of syntactic variation and change, in syntactic reconstruction, in the use of electronic corpora in historical linguistics, as well as the historical syntax of individual languages. My previous research projects include the Historical Corpus of the Welsh Language, the Syntactic Atlas of Welsh Dialects, the History of Negation in the Languages of European and the Mediterranean, and the History of pronominal subjects in the languages of northern Europe. I am currently working on projects to map dialect variation using social-media data and to create Curlew, a new atlas of linguistic variation in England and Wales.