Dylan Wiliam is one of the world's leading authorities on the ways that assessment can be used to improve student learning and has authored or co-authored over 300 articles, books, and book chapters on education. After 7 years teaching English, mathematics and science in urban secondary schools in London, he joined Chelsea College,University of London, which later merged with King's College London. During his time at King's College London, he ran the mathematics teacher education programme, co-ordinated a large scale testing programme, served for five years as Dean of the School of Education and from 2001 to 2003, was Assistant Principal of the College.