Somewhere in my reading I read an explanation for the Celtic Cross (a
regular Roman cross with a circle around the intersection): the circle
is an ancient Celtic symbol for protection around Jesus' head; the head
being the source of life and therefore of utmost importance to the Celts.
But, for the life of me I can't remember where I read that.
Maybe in Lloyd Laing's "Celtic Britain" but I can't find it in there/