‘Boo!’ came a voice from the stalls. ‘Boo. Outrage!’ It was hard not to feel a pang of admiration. British opera audiences don’t tend to boo; we’re either too polite or too unengaged. But there we were in Act Three of Kirill Serebrennikov’s production of The Marriage of Figaro – just after the scene where Susanna, the Count and the Countess enjoy a three-in-a-bed romp while singing the trio ‘Soave sia il vento’ – and at least one person felt passionate enough to raise his voice.