Sometimes if you go to Mass in the Cathedral at 10.30, the light shining in through the East Windows on a winter’s morning slants in from a low sun directly into one’s eyes. Everything in the sanctuary becomes indistinct. In the Christmas season all you can make out is the vague shape of the Christmas trees. As you watch, altar, priest vanish and then only the words can be heard, in Advent of the Incarnation and Mary’s acceptance and at the Consecration only the Host raised high emerges from the encircling gloom.

Strangely, almost magically lit by the light behind as in some complex stage lighting, but it is only the Sun; and now the Sun continues its course, passes the window and the white scene is restored to its ordinary, everyday colours.