“Look at our opera stages: underused and unloved, the understudy who triumphs is rare. Why? because they have so few opportunities. Typically, operas run for six or seven performances across two months, compared with the nightly schlepp of a West End hit. Of course, opera singers do fall ill, but even then an understudy can be denied his or her chance. Covent Garden, for instance, will jet in a big-name singer when there’s a perfectly adequate understudy waiting in the wings.”