In the Middle Ages, especially north of the Alps, the day was a festival of inversion involving role reversal between children and adults such as teachers and priests, with boy bishops presiding over some church services. Bonnie Blackburn and Leofranc Holford-Strevens suggest that this was a Christianized version of the Roman annual feast of the Saturnalia (when even slaves played "masters" for a day). In some regions, such as medieval England and France, it was said to be an unlucky day, when no new project should be started.