The exact date of the unit's establishment is uncertain: the Vita Ignatii, an hagiographic account of the life of Patriarch Ignatius of Constantinople, records that the unit was said to have been established circa 809 by Emperor Nikephoros I (r. 802–811), and this date is generally accepted; sigillographic evidence, however, is vague, and could support a late 8th-century establishment.
In conjunction with Andreas Rass, afterwards Bishop of Strasbourg, he revised, enlarged, and translated several apologetic, dogmatic, homiletic, and hagiographic works, the best known of which are an enlarged German edition of Butler's "Lives of the Saints" (24 vols., Mainz, 1821-27), translations from the French of Carron, Brillet, Picot, and others, and an extensive compilation of sermons by various authors.
According to his hagiographic Life, completed in 884 by a Breton monk named Wrmonoc of Landévennec Abbey, Paul was the son of a Welsh chieftain named Perphirius/Porphyrius ("clad in purple"), from Penychen in Glamorgan.