GLASS/LIGHT, an exhibition co-curated by Brian Clarke, John Piper and Martin Harrison in 1978, offered a comprehensive survey of twentieth-century stained glass. Collaborating with artist Marc Chagall, the exhibition was a major part of the 1978 Festival of the City of London, drawing an attendance of approximately 20,000 people. GLASS/LIGHT, held at the Royal Exchange, was the most extensive exhibition of its kind to date, featuring exhibits from all over Europe spanning from the 8th to the 20th century.