Paulus was the name of an imperial notary, or senior civil servant, who served under the Roman Emperor Constantius II in the middle of the 4th century. He is described by the historian Ammianus Marcellinus, who probably met him. According to Marcellinus, his cruelty was infamous throughout the Roman world. He was dispatched to Roman Britain by the Emperor Constantius II to control subversive elements in 353, after the fall of the Britto-Frankish usurper Magnentius. So harsh were his measures that he earned the nickname Catena meaning 'The Chain', because he chained many people and dragged them with their chains through the streets.
His brief in Britain was to hunt down known supporters of the recently-defeated usurper Magnentius in the army garrisons in Britain. According to Marcellinus, once Paulus arrived, he widened his remit and began arresting other figures, often on apparently trumped-up charges and without evidence. Paulus' methods were so extreme and the injustices he committed so great, however, that eventually the vicarius of Britain, Flavius Martinus, although a loyal supporter of Constantius, felt obliged to end them. He tried to persuade Paulus to release the innocent prisoners he had taken using the threat of his own resignation as leverage. Paulus refused, however, and turned on Martinus, falsely accusing him and other senior officers in Britain of treason. In desperation, Martinus attacked Paulus with a sword. However, the attack failed and the vicarius committed suicide. The emperor then sent him to Egypt with the excuse that the consultations to and responses from the oracle of Besa had displeased him. Paulus set up a kangaroo court and with near full imperial power delegated to him, he began summarily passing judgement on suspected traitors.
Ammianus Marcellinus tells us that in 355 he was ordered to hunt down the followers of another Frankish usurper called Claudius Silvanus. Again he tortured and killed people.
According to Ammianus Marcellinus, Paulus was condemned to death by the Frank Arbitio at the Chalcedon tribunal under Constantius' successor, Julian the Apostate, in late 361, or early 362. He was burned alive.