The Greek historian Sozomen speaks of Constantine living in Gaul and Britain, and there, as, he says, was universally admitted, becoming a Christian. Both Eusebius, writing about 320, and Sozomen, about 443, tell of an experiment made in the palace by Constantine's father Constantius, when he governed Gaul and Britain, which shews the spread of the gospel and the high places it had by that time reached. It has this special interest for Britain, that York was one of the two cities at one of which it must have taken place, Trèves being the other; for those were the two capitals and seats of government of the whole province of the Gauls, the one for the continental the other for the insular department of the province. A persecution of the Christians was ordered by his three colleagues in the empire, about the year 303. Constantius, though not himself a Christian, did not allow much severity in his own government; a contemporary writer, Lactantius, declares that from east to west three savage beasts raged; everywhere but in the Gauls, that is, Gaul and Britain. The experiment was this. He told the officers of his court, who are spoken of as if all were Christians, though he himself was not, that those of them who would sacrifice to demons should remain with him and enjoy their honours: those who would not, should be banished from his presence. He gave them time to think the matter over. They came to him again, each with his mind made up; and some said they would sacrifice, and some said they would not. When all had declared their intention, he told those who would sacrifice, that if they were ready to be false to their God, he did not see how he could trust them to be true to him. To the others he said that such worthy servants of their God would be faithful to their king too. The story reminds us of the sturdy old pagan king of Mercia, Penda, who said he was quite willing that the Lindisfarne missionaries should convert his people to Christianity, if they could; but he gave full warning that he would not have people calling themselves Christians and not living up to their high profession.