For the first 20 years of his career Paul worked in research and undergraduate teaching in physics. During this time he also became involved in assessment work, both as a member of the JMB schools examination board and in a study of assessment of university physics degrees. This move from physics research to work in science education was accelerated when he became joint organizer of the innovative Nuffield A-level physics course, and was completed when he moved in 1976 from his physics chair in Birmingham to a chair in science education in London, initially at Chelsea College and subsequently at King’s. There his curriculum development work with the Nuffield Foundation developed further to include design and technology, and science work at primary, secondary and tertiary levels. Paul was chair of the government’s Task Group on Assessment and Testing in 1987-88, and deputy chairman of the National Curriculum Council from 1989 to 1991. This stimulated interest in the formative aspects of assessment. A published review of assessment work in science education led to an invitation from the Assessment Reform Group to produce, in collaboration with Dylan Wiliam, the more comprehensive review of formative assessment published in 1998. Since then he has been engaged in research and in development work to improve classroom practices in both formative and summative assessment, some of it linked to work as a member of the Assessment Reform Group. One feature of his work has been to engage closely with and for classroom teachers, by publications, notably the Black Box series of booklets, and by many contributions to INSET programmes. Paul has served on three committees of the USA National Research Council, and is currently a member of the Technical Advisory Group of OFQUAL.