To mark the 70th anniversary of Glyndebourne Festival Opera, James Naughtie explores the unique spirit of the Glyndebourne experience through the eyes of directors, conductors and members of the chorus spending their first full season at the Sussex opera house and then on the company's annual tour. How is the 21st-century opera house trying to live up to its founder John Christie 's dictum, that Glyndebourne should do "not only the best that we can do, but the best that can be done anywhere"? producer Margaret Budy