The monks sent to England by Pope Gregory the Great soon came to see that the Celtic Church differed from theirs in many respects. Augustine himself, having concluded an alliance between Ethelbert and the Roman See, held several conferences with the Christian Celts in order to accomplish the most difficult task of their subjugation to Roman authority. These differences were largely ritualistic and disciplinary. The Celtic Christians celebrated Easter according to the calculation of Sulpicius Severus, while the Romans had another mode of computing the proper day.[237:1] The Celts appealed to St. John, the Romans to St. Peter.[237:2] The Celtic Church might be called a monastic Church, since the abbot ruled over the bishop.[237:3] The Celts shaved the front of the head from ear to ear as a tonsure, while the Romans shaved the top of the head leaving a "crown of thorns."[237:4] The Celts permitted their priests to marry, the Romans forbade it. The Celts used a different mode of baptism from that of the Romans, namely, single instead of trine immersion. The calendar for all movable festivals was not the same. The Celts held their own councils and enacted their own laws, independent of Rome. The Celts used a Latin Bible unlike the Vulgate, and kept Saturday as a day of rest, with special religious services on Sunday.[237:5] Notwithstanding these variances, which do not seem to be at all on the fundamentals, there were many doctrinal and constitutional resemblances. Both churches were orthodox; both used a Latin ritual[238:1]; both had developed an episcopal organisation; both believed in monasticism; and both were actively engaged in missionary work. Nevertheless the British Christians looked with much disfavour upon the Augustine mission to convert their pagan conquerors and oppressors.