H.H. Scullard writes that "he promised to follow the Augustan model in his principate, to end all secret trials "intra cubiculum", to have done with the corruption of court favorites and freedmen, and above all to respect the privileges of the Senate and individual Senators." His respect of the Senatorial autonomy, which distinguished him from Caligula and Claudius, was generally well received by the Roman Senate. Scullard writes that Nero's mother, Agrippina, "meant to rule through her son." Agrippina murdered her political rivals: Domitia Lepida the Younger, the aunt that Nero had lived with during Agrippina's exile; Marcus Junius Silanus, a great grandson of Augustus; and Narcissus. One of the earliest coins that Nero issues during his reign shows Agrippina on the coin's obverse side; usually, this would be reserved for a portrait of the emperor. The Senate also allowed Agrippina two lictors during public appearances, an honor that was customarily bestowed upon only magistrates and the Vestalis Maxima. In 55, Nero removed Agrippina's ally Marcus Antonius Pallas from his position in the treasury. Shotter writes the following about Agrippina's deteriorating relationship with Nero: "What Seneca and Burrus probably saw as relatively harmless in Nero—his cultural pursuits and his affair with the slave girl Claudia Acte—were to her signs of her son's dangerous emancipation of himself from her influence." Britannicus was poisoned after Agrippina threatened to side with him. Nero, who was having an affair with Acte, exiled Agrippina from the palace when she began to cultivate a relationship with his wife Octavia. Jürgen Malitz writes that ancient sources do not provide any clear evidence to evaluate the extent of Nero's personal involvement in politics during the first years of his reign. He describes the policies that are explicitly attributed to Nero as "well-meant but incompetent notions" like Nero's failed initiative to abolish taxes in 58. Scholars generally credit Nero's advisors Burrus and Seneca with the administrative successes of these years. Malitz writes that in later years, Nero panicked when he had to make decisions on his own during times of crisis. "The Oxford Encyclopedia of Ancient Greece and Rome" cautiously notes that Nero's reasons for killing his mother in 59 are "not fully understood." According to Tacitus, the source of conflict between Nero and his mother was Nero's affair with Poppaea Sabina.