At the heart of the evening was Joyce El-Khoury, who joined rehearsals only a couple of weeks ago but had just one week to learn the formidable role of Hélène. You'd never have guessed. Singing with fearless attack in her boléro Merci, jeunes amies and bringing warmth and poise to her later scena with Henri, she gave a performance of staggering assurance and stamina. To step in under such circumstances would have been achievement enough; to deliver at this level felt almost superhuman.