He assisted Claudius in his literary, judicial and historical pursuits as a researcher before the emperor's accession and this became Polybius' official role in the imperial bureaucracy, with the title a studiis.
[1] Suetonius, the biographer and secretary to the Emperor Hadrian, claims that Claudius was so appreciative of his help that Polybius was allowed to walk between the consuls when on official business.
[2] When Polybius lost a brother in the early 40s CE, Seneca the Younger, (who was then in exile,) wrote his famous Ad Polybium in response.
He was executed for crimes against the state, supporting the view that freedmen were still in a position inferior to emperor, whatever their influence.
Ancient historians claimed that Empress Messalina arranged for his death when she tired of him as a lover.