My son was surprised I had never seen the Chapter house thinking it was accessible, but it turns out only to folks like him with a key. Next time; these are through the iron grille, but the glass looked special and is byChristopher Whall, 1903 http://www.gloucestercathedral.org.uk/history-heritage/architecture/stained-glass/arts-crafts-9616.php
copyright; please look at ORIGINAL size