In 1978 he started working at the University of Cambridge Computer Laboratory as assistant lecturer under Maurice Wilkes and Roger Needham in the Computer Laboratory, and worked with others on the "Cambridge Model Distributed System". In 1985 he left Cambridge to found his own contract research company (Architecture Projects Ltd – APM Ltd), which led projects to develop ANSA, the Advanced Network Systems Architecture. In 1996 he had founded another sister company called Digitivity to develop a product to enable the secure deployment of Java clients for business-to-business applications. Two years later he joined Citrix Systems Inc. following their acquisition of APM and Digitivity to become Director of Advanced Technology. In 2001 he joined Microsoft Research in Cambridge as an assistant director, and became managing director in April 2003. In 2010 he became chairman of Microsoft Research EMEA. He retired from Microsoft in September 2011.