I just saw on Wikipedia that some Byzantine Emperors were still using what I think is the 'Roman naming convention' ie, Justinian I's name was Flavius Petrus Sabbatius Iustinianus, Constantine I was Gaius Flavius Valerius Aurelius Constantinus.
Was this naming convention still in use during the 9th century ? Were the name rather in their latin (as shown on Wikipedia) or in their greek version ?