The Choir of King's College, Cambridge
Form the Your Tube notes:
In this arrangement this is sometimes called the Herefordshire Carol as the tune was collected by Vaughan Williams at King's Pyon in that county. Otherwise, and in the longer version collected by Sharp, it is often known by its first line: 'This Is the Truth Sent From Above'.
When Vaughan Williams is sung at church, it is always a good day.