The most demanding performance of the musical year

The annual Christmas Eve carol service from King's College Chapel begins with a boy soprano singing the first verse of "Once In Royal David's City". I learn from an interview with a couple of former choristers that all the boys actually practise this number. The actual singer is only chosen when the red light goes on to begin the broadcast. The choirmaster points at one boy and off he goes. No time for nerves, presumably.

Happy Christmas.