Agrippa's friendship with Augustus seems to have been clouded by the jealousy of Augustus' nephew and son-in-law Marcus Claudius Marcellus, which was probably instigated by the intrigues of Livia, the third wife of Augustus, who feared Agrippa's influence over her husband. Traditionally it is said the result of such jealousy was that Agrippa left Rome, ostensibly to take over the governorship of eastern provinces – a sort of honourable exile, but he only sent his legate to Syria, while he himself remained at Lesbos and governed by proxy, though he may have been on a secret mission to negotiate with the Parthians about the return of the Roman legions' standards which they held. On the death of Marcellus, which took place within a year of his exile, he was recalled to Rome by Augustus, who found he could not dispense with his services. However, if one places the events in the context of the crisis of 23 BC it seems unlikely that, when facing significant opposition and about to make a major political climb down, the emperor Augustus would place a man in exile in charge of the largest body of Roman troops. What is far more likely is that Agrippa's 'exile' was actually the careful political positioning of a loyal lieutenant in command of a significant army as a backup plan in case the settlement plans of 23 BC failed and Augustus needed military support. Moreover, after 23 BC as part of what became known as Augustus' "Second Constitutional Settlement", Agrippa's constitutional powers were greatly increased to provide the Principate of Augustus with greater constitutional stability by providing for a political heir or replacement for Augustus if he were to succumb to his habitual ill health or was assassinated. In the course of the year, proconsular imperium, similar to Augustus' power, was conferred upon Agrippa for five years. The exact nature of the grant is uncertain but it probably covered Augustus' imperial provinces, east and west, perhaps lacking authority over the provinces of the Senate. That was to come later, as was the jealously guarded tribunicia potestas, or powers of a tribune of the plebeians. These great powers of state are not usually heaped upon a former exile.