His broad research interests are computational and theoretical linguistics and automated speech and language processing. He directed and was heavily involved in the teaching of the MPhil in Computer Speech, Text and Internet Technology, taught jointly with the Engineering Department. He currently teaches similar modules as part of the department's MPhil in Advanced Computer Science.
From 1990 until 1996 he was an EPSRC Advanced Research Fellow undertaking research at Macquarie University in Sydney, University of Pennsylvania in Philadelphia and Xerox European Research Centre in Grenoble, as well as at the Computer Laboratory.
His specific research interests include (nearly-)deterministic, statistical, and robust parsing techniques, acquiring lexical information from electronic textual corpora and dictionaries, defaults and constraint-based approaches to linguistic description, exploiting prosody and punctuation during parsing, models of human language learning and parsing, and evolutionary simulations of language variation and change.
He has developed numerous applications building on this research through iLexIR Ltd, a consultancy company he cofounded in 2004 -- for example, automated assessment of and error detection in English language learners' texts. In 2009, iLexIR spun-out Swiftkey, maker of the world's most popular predictive keyboard for smartphones. In 2013, he co-founded English Language iTutoring Ltd and was its chief scientist until 2019.
He has published over 100 research articles and four books. He has been been Principal/Co-Investigator or Coordinator of seventeen EU and UK funded projects since 1985. He was a senior editor of Computer Speech and Language and was founding director of and is a Principal Investigator in the Automated Language Teaching and Assessment (Alta) Institute.