Christmas is a time when people want to hear a decent choir, and it’s the time when decent choirs sweep by the coachload into London for the spotlit choral platform that St John’s Smith Square runs throughout the festive period.

Night after night they come, doing the standard repertoire of awestruck shepherds, Virgin Births and wassailing (a word that passes no one’s lips except in late December) with excursions into less familiar territory, some of it new, some old. And it provides a chance you wouldn’t get at any other time of year to make comparisons: a choral stock-take of who’s doing well, who’s struggling to keep up, who has real ambition as opposed to marking time. And the results can be surprising.