Professor Margaret Deuchar’s current research interests are in code-switching. With a research team at Bangor University she collected bilingual conversations from three groups of bilinguals: Welsh-English, Spanish-English and Welsh-Spanish. The conversations were transcribed and are made available in the public domain (www.bangortalk.org.uk). Data from the corpora have been used by Margaret’s collaborators and herself to evaluate competing linguistic theories of code-switching (e.g. Herring et al 2010), to compare code-switching patterns in three bilingual communities (Carter et al 2011), challenge influential views of the boundary between code-switching and borrowing (Stammers & Deuchar 2012) and to establish the key extralinguistic factors influencing the production of code-switching. Margaret is providing advice on developing a framework for data collection and on tagging Welsh corpus data.