Under the Roman Emperor Nero, Serenus was entrusted with the office of praefectus vigilum, i.e. he was the chief of the Roman fire brigade, which kept watch at night all over the city and ensured that fires that frequently broke out in Rome were quickly extinguished.
[1] Under Emperor Claudius – as mentioned by the historian Tacitus – Decrius Calpurnianus was still chief of the fire guard.
In Seneca's treatise "On the Tranquillity of the Soul" (De Tranquillitate Animi), a letter from Annaeus Serenus to Seneca is reproduced at the beginning, from which it becomes apparent how much Serenus was attracted to a simple life of moderation, and at the same time how much he was irritated by the hectic pursuit of state positions of honour and a life of luxury that he observed all around him.
While Serenus was initially close to Epicurean thought, under Seneca's influence he moved closer to the philosophy of the Stoa and decided to remain at the imperial court.
As Tacitus reports, Serenus played a helpful role in the young Emperor Nero's love affair with the freedwoman Claudia Acte by providing the Emperor's favourite, who suffered under the surveillance of his mother Agrippina, with the latter's secret gifts.