Burrus came from Gallia Narbonensis and held commissions in the Roman army and posts in the households of Livia (widow of the emperor Augustus) and the emperors Tiberius and Claudius. Made prefect of the Praetorian Guard in 51, he owed his promotion to Claudius' wife, Agrippina, who had become the dominant influence on her husband. Agrippina doubtless counted on Burrus' continuing support, but, after the accession of the 16-year-old Nero, Burrus, in concert with Seneca, managed to subvert her power. It is reasonable to suppose that until Burrus' death in 62, he and Seneca were responsible for imperial policy and administration. The ancient allegation that Nero poisoned Burrus can be neither proved nor refuted. (Encyclopedia Britannica)
Praetorian prefect (51-62) and, with Seneca, the chief adviser of the Roman emperor Nero (reigned 54-68).