As Tribune and a man of military experience, Flavus enjoyed great significance in the plot. Along several others, including the Centurion Sulpicius Asper, Flavus is described as one of the conspiracy's "leading lights" by Tacitus.^[2] He was close to Gaius Calpurnius Piso, the figurehead of the conspiracy.

Tacitus observes that Flavus' hatred for Nero arose suddenly while he was watching him perform on stage but failed to attack him in front of the audience because he would not have had a chance to escape.^[3]

Tacitus also observes that it was rumoured that, after the success of the conspiracy, Flavus intended to murder Piso and give control over the empire to Seneca the Younger, a fellow conspirator, because "it mattered not as to the disgrace if a harp-player were removed and a tragic actor succeeded him." For as Nero used to sing to the harp, so did Piso in the dress of a tragedian".^[4]

Questioned by Nero as to the motives which had led him on to forget his oath of allegiance, "I hated you," he replied; "yet not a soldier was more loyal to you while you deserved to be loved. I began to hate you when you became the murderer of your mother and your wife, a charioteer, an actor, and an incendiary."^[5]

Flavus, like Seneca the Younger, is presented as a bastion of traditional morality by Tacitus, as in the above quote, because of his stand against Nero's excesses. The Classicist Edward Champlin argues that Flavus is one of the few figures in the Annals whom Tacitus eulogises without reserve.^[6]

Because of his involvement in the conspiracy, Flavus was condemned to death. He was beheaded in two strokes in front of a pre-dug pit near the Castra Praetoria in 65 CE.^[7] The execution was entrusted to a tribune, Veianius Niger.^[8]