Tavius was a high-ranking member of Emperor Nero's court in Rome. Secretly a Christian, he and Maximus Pettulian plotted to kill Nero in 64.
He tried to purchase Barbara Wright as a slave after seeing her concern for a fellow slave, but was told by Sevcheria that he could only bid for her at the slave auction. At the auction, he bid ten thousand sesterce for her and took her back to Nero's palace to serve the Empress Poppaea.
Tavius met with the First Doctor, whom he believed was Pettulian. He discussed his plans with the Doctor, to the Doctor's confusion.
Poppaea, jealous of Barbara, ordered Tavius to dismiss her. Tavius saw this as an opportunity to help Barbara escape. On Barbara's information, he warned the Doctor that Nero wanted to make him fight in the arena. He later encountered Ian Chesterton in the palace and helped him reunite with Barbara, and then helped them escape. (TV: The Romans)