The choirboys at King's College Chapel in Cambridge have a more nerve-wracking Christmas than most.

One of them will be picked to sing the solo for Once in Royal David's City in the Nine Lessons in Carols service that gets broadcast around the world on Christmas Eve - but they will only find out seconds before they're supposed to sing.

The choirmaster judges who is in good voice on the day - and points at his selected soloist as the broadcast starts.

Rupert Peacock is one of the only boys to have sung the solo so often as a choirboy - twice on the radio and once on the television. Hear him speak about Christmas' most terrifying solo.

Producer: Sophia Smith Galer

(Photo credit: BBC)