Oaths

In Poul Anderson's The Sign Of The Raven (New York, 1980), Harold of England, an enforced guest of William of Normandy, swears on a consecrated jewel to uphold William's claim to the English crown. "William's half brother, Bishop Odo the crafty..." has hidden saintly relics under the jewel to make the oath even more binding (p. 134).

Harold, returned home, rightly argues that:

" 'A forced oath is no oath...' " (p. 135)

- and gets Bishop Wulfstan to absolve him of the oath. I agree that Odo was dishonest but are he and Wulfstan anything more than political tools of the rulers of Normandy and England respectively? In these circumstances, how could the Church claim to be an independent agent?