Procopius of Caesarea was the security and legal advisor to Flavius Belisarius. He was known to the Fifth Doctor as an important historian, the writer of the Wars of Justinian and the Secret History, where he recounted events as he himself experienced them.
In 540, he accompanied Belisarius to Ravenna. He hid behind the TARDIS to escape the fight. He told Vicki Pallister at length about the Battle of Ad Decimum, which led to the capture of Carthage. He was also present for the siege of Rome. At this time, he hadn't written any historical works. (AUDIO: The Secret History)