Britain was now divided into four Diocletian provinces, to which a fifth--Valentia--was later added when the country north of Hadrian's wall was re-occupied. The only other event of Diocletian's reign to be noticed is the persecution of Christians in which, according to tradition, St. Alban lost his life at Verulam about 303. (19-20) On May 1, 305, Diocletian and Maximian abdicated. Constantius and Galerius now became Augusti. Trouble arose over the two vacant Cæsarships. It was the aim of Galerius to exclude Constantine, but the latter escaped to his father's camp at York, a few weeks before Constantius died on July 25, 306, after a victory over the Picts and Scots. Constantine was in power under various titles in Gaul and Britain for five years until, in 311, when Galerius died, he began his march on Rome, during which he is said to have had his vision of the cross with the words [Greek: en toutô nika]. In 314 the bishops of York, London, and some other uncertain British see attended the Council of Arles which sat to deal with the Donatist schism. The British Church was also represented at the Council of Nicæa, called by Constantine in 325 to consider the Arian heresy, when the Nicene Creed in its original form was authorized; the British vote was orthodox. It was Constantine who in 321 first made Sunday a holiday, but whether Christianity or Mithraism prompted him to this is doubtful. (22-23) When Constantine the Great died in 337 the empire was divided between his sons. Constantius II. received the east; Constans, Africa, Italy, and the Danuvian region; Constantine II., Gaul and Spain. In 340 Constantine II. attacked Constans and was killed. Constans then ruled the united west; it seems that Constans and Constantius II. visited Britain in 343. Constans was assassinated in 350; this left Constantius II. alone. His policy of toleration towards the Arians led to a great Church Council in 359. The eastern bishops met at Seleucia, the western at Ariminum, where Britain was represented. By a certain amount of coercion Constantius forced his views on the Western Council. At this time the prosperity of Britain was great and corn was exported in large quantities. (24) In 367 Valentinian I. made his son Gratian, Augustus. Gratian was later married to Constantia, daughter of Constantius II. Roman power was now asserted once more against the Picts and Scots, and also against the Saxon raiders by Theodosius, whose son became Augustus in 379. Gratian himself was occupied on the Continent. In 383 Magnus Maximus was proclaimed emperor in Britain, and Gratian was murdered on August 25.