accusations against senators during these years. The emperor could intervene to exercise the imperial virtue of dementia-, in a.d. 22 he allowed Decimus Iunius Silanus to return from the exile that had been forced upon him when Augustus had revoked his amicitia because of Decimus' association with the younger Iulia during the crisis of a.d. 8. Tiberius did not, however, feel that Decimus could be allowed to return to public life.[414]
Another important effect of Tiberius' absences from the capital was to increase the importance of Aelius Sejanus, now the sole praetorian prefect, as the channel of communication between senators and the emperor. During these years Sejanus greatly strengthened his police powers in Rome by concentrating the praetorian cohorts in a single, permanent camp (one of the first military camps to have a permanent stone wall). There is no reason to believe that the immediate objective was anything more sinister than to impose better discipline on the soldiers; but the camp was also a suitable place to keep political prisoners.
The death ofDrusus on 14 September a.d. 23 ended for the time being any hopes Tiberius had of leaving his power in the hands of a son, natural or adopted, who would be old enough and experienced enough to rule. Perhaps Drusus would not have been an ideal emperor. Like his father, he was a heavy drinker; it was said that he had once physically attacked Sejanus during a drinking party. The story was one of the arguments later advanced in support of allegations that Sejanus had poisoned Drusus, but these inventions postdated Sejanus' fall; the two had been loyal colleagues and friends for many years, and the summer of a.d. 23 was another particularly unhealthy one. Tiberius made a point of being present in Rome to give the funeral speech.
The question of the succession was now open again. By early a.d. 23, two of Germanicus' sons had already come of age; to strengthen their position, their mother Agrippina asked Tiberius to provide her with a new husband. It is possible that she had Asinius Gallus in mind. One of his sons, Asinius Saloninus, had been betrothed to a daughter of Germanicus, but died in a.d. 22, before the marriage could take place; two other sons of Gallus were consuls during these years, C. Asinius Pollio in 23, and Marcus Asinius Agrippa in 25 (but he died in the following year). Tiberius would not allow Nero and Drusus to come under the protection of such a powerful stepfather, particularly one whom he loathed.
The emperor's concern that Germanicus' sons might replace him was shared by the praetorian prefect Sejanus. Sejanus' own interest in Tiberius' survival was illustrated by an incident in a.d. 26.21 While Tiberius was on his way to his villa at Capri, part of the ceiling of a grotto near Terracina collapsed on the imperial party during a dinner. Sejanus threw himself upon Tiberius, convincing him of the genuineness of his loyalty. In the previous year Tiberius had had doubts about Sejanus: he refused a request that he should be allowed to marry Drusus' widow Livilla (Livia lulia). Sejanus may have been a loyal supporter of the dynasty, like his father and perhaps grandfather before him, but that did not give him sufficient status to rank with the republican nobility. Even his wife's family had only been consular for one generation. In Tiberius' opinion, Sejanus would not have had the political influence needed to protect Tiberius Gemellus against the claims of Agrippina's children. In any case, he had every intention of remaining alive for many years to come, and was supported in this by the prognostications of his personal astrologer Thrasyllus.
Tiberius had been 66 in the previous November. At an age when other Roman senators could look forward to retiring from public life, he saw no escape from the responsibilities inherited from Augustus. It is not surprising that he should have preferred to stay away from Rome, even for the funeral of his mother Livia in a.d. 29. The question of the succession will have been a major source of conflict between mother and son; Tiberius Gemellus was Livia's great-grandson, but so (through Drusus) were Agrippina's three sons, and Augustus had clearly indicated in his will that the succession should ultimately go to them. So long as Livia was alive, she could protect them against Tiberius' displeasure. Livia's funeral oration was given by Gaius Caligula, whom Livia had taken into her own domus. Soon after the funeral, Sejanus hadAgrippina, Nero and Drusus arrested. Caligula had not been allowed to don the toga virilis yet, and consequently could not be treated as a political threat. He moved to the house of his grandmother the younger Antonia, who protected the interests of the supporters of her son Germanicus as well as she could during the years of Sejanus' supremacy.
Following her funeral, Livia was awarded full divine honours by the Senate, similar to those awarded to her husband on his death (there were minor differences, as protocol required; for instance the image of the divus was carried by a four-horse chariot, while the diva Augusta had to be satisfied with two horses). Her will was notable for the enormous legacy she bestowed on the young Servius Sulpicius Galba (born j B.C.); a relative of Livia's, Livia Ocellina, was his stepmother and had adopted him. Tiberius was understandably upset by the size of the legacy - 50 million sesterces — and apparently held back even the revised sum of
21 Stewart 1977 (f 583).
500,000 he was prepared to countenance. Galba's elder brother (cos. a.d. 22) had already attracted his disfavour, and was later forced to commit suicide (с. a.d. 36). Livia's legacy demonstrated both her displeasure at her son and a belief that Galba was worthy of holding a central position on the public stage. After Livia's death, Galba had the support of Antonia (and later of Caligula). His wife was probably the daughter of M. Aemilius Lepidus, capax imperii, the consul of a.d. 6; another of Lepidus' daughters married Drusus, son of Germanicus. Galba himself had already won the praetorship (it is not certain in what year he held it, but we are told of the tightrope-walking elephants he presented at the Floralia). In a.d. 33, he was consul ordinarius. It is not surprising that Tiberius, having worked out his horoscope, should have said that the young Galba was destined to be emperor one day.
Although Tacitus insinuates that one of Tiberius' main motives for leaving Rome had been to avoid his mother, her death made him no more willing to return. His absence did not mean that he ceased to control the empire; but it allowed Sejanus to monopolize the information and advice about events in the capital on the basis of which Tiberius' decisions were taken. Sejanus had already made clear to the emperor his readiness to marry Drusus' widow Livilla, and thus immediately become the stepfather of Tiberius' grandson and intended successor, and in due course perhaps the father of further children who would be eligible for imperial office. So long as Sejanus' stepson, or his own children, were still too young for this office, he could fulfil the role that Augustus had intended Tiberius to play for Germanicus. Tiberius understood this ambition, though it is not clear whether he was now prepared to allow the marriage.[415] What he did do was appoint Sejanus, although he was not a senator, consul ordinarius for a.d. 31, and he publicly demonstrated the extent to which the praetorian prefect was 'partner of his labours' by holding his own fifth consulship as Sejanus' colleague. His third consulship had been held with Germanicus, his fourth with Drusus: in both cases this was a way of indicating who was the heir- apparent. Sejanus' election was held on the Aventine hill, traditionally associated with the urban plebs, and the gifts and shows granted on this occasion were for them a welcome contrast to the neglect which Tiberius' electoral reforms had occasioned, since such bids for popularity now normally had little point.[416]