Well, we have Floki and Rollo, who are going to be there as well, even if not in the church; they will be able to tell Athelstan about the bishop -- perhaps triumphantly, claiming Ragnar for paganism after all because he didn't hesitate to kill a 'man of god'. Then Ragnar will explain about killing one to be able to spare everybody else, and about the bishop telling him he'll go to hell. Anybody who comes between him and Athelstan meets a sticky end...