This song is called Silent Falls The Winter Snow and appears in the beautifully animated The Tailor Of Gloucester, by Beatrix Potter.
It is sung by St. Alban's Abbey Boys' Choir conducted by Barry Rose.
'Silent falls the winter snow, the air is crisp, and the fires glow. Of all the splendour in our town, the holy cathedral wears the crown. Christmas day, when the children do sing 'Open the door and let us come in', for on this day is born a king, and joyous voices are praising. Glory, glory He is crowned, the cathedral glows as the voices sound. The joy and wonder fill the air, as hearts are lifted in Christmas fair.'
Song by Colin Towns from the album The Beatrix Potter Music Collection.