Professor Sarah Brown is a renowned expert on medieval ecclesiastical architecture, stained glass history and conservation, and is the author of many books and articles in the field. Sarah is a Senior Lecturer specialising in stained glass in the History of Art Department at the University of York, and since 2008 has also been Director and Chief Executive of the York Glaziers Trust, responsible for the care of the stained glass of York Minster and for projects for external clients throughout the UK. Her previous publications for include The Great East Window of York Minster: An English Masterpiece.Christopher Norton is a Professor in History of Art at the University of York and a member of the Centre for Medieval Studies.