Christianity had been known in Britain among the Celts since the third century, but in the fifth century the southeast was invaded by pagan Anglo-Saxons who drove the Celts north and west into Scotland, Ireland, and Wales. Ethelbert succeeded his father as Saxon king of Kent in 560. He was, according to the Venerable Bede, a fair ruler and the first English King to promulgate a code of law. Brisk cross-channel trade with France exposed Ethelbert to Roman customs and luxuries. His admiration for the Frankish ways led him to marry a French Christian princess, Bertha. Although not a Christian himself, Ethelbert promised Berthas father that she could practice her faith. Good to his word, he welcomed her chaplain and granted him an old Christian mausoleum to convert into the Church of St. Martin, which still stands today.