For a time, he was considered his father's heir, but that changed after his mother's downfall in 48, when it was revealed she had engaged in a bigamous marriage without Claudius' knowledge.

The agnomen, his first surname Germanicus, was first awarded to his paternal grandfather, Drusus the Elder, after his death in 9 BC to commemorate his victories over the Germanic tribes.

To mark the birth, the emperor issued sestertii with the obverse Spes Augusta, the hope of the imperial family.

Gaius Suetonius Tranquillus, a Roman historian, wrote from the late first century that Claudius adored Britannicus; carried him around at public events; and "would wish him happy auspices, joined by the applauding throng".

His tutor then, as part of his mother's contrivances, told the emperor of Decimus Valerius Asiaticus's involvement in the murder of Caligula and of his growing popularity in Rome.

[10][11] It was later voted by the Senate for Sosibius to be given a million sesterces for giving Britannicus the benefit of his teachings and Claudius that of his counsel (his involvement in the case against Asiaticus).

Claudius watched the young nobility, including Britannicus and Domitius, enact the Battle of Troy in the circus.

[14] He says:[15] She had grown so frantically enamoured of Gaius Silius, the handsomest of the young nobility of Rome, that she drove from his bed Junia Silana, a high-born lady, and had her lover wholly to herself.

Silius was not unconscious of his wickedness and his peril; but a refusal would have insured destruction, and he had some hope of escaping exposure; the prize too was great, and so he consoled himself by awaiting the future and enjoying the present.

Claudius thought that marrying his niece would bring his family closer to that of Augustus, as Agrippina and Domitius were the last living descendants of Germanicus.

[5] It was in 53 that Nero married Britannicus' sister Octavia, who first had to be legally transferred to another family to obviate charges of incest.

According to Suetonius, when Claudius mentioned his intention to give Britannicus the toga of manhood, he said, "That the Roman people may at last have a genuine Caesar.

"[32][33][34] The actions that Claudius took to preserve his rule in the short term were not easily undone as Britannicus approached manhood.

Suetonius reports that Claudius now admonished his son to grow up quickly, which implied that everything would be righted when he assumed the toga virilis.

[35] Unfortunately for his cause, Narcissus was away in Campania when the emperor was poisoned, and Britannicus and his sisters, Octavia and Antonia, were kept out of sight in their rooms by Agrippina.

If one thought that Britannicus' claim should take precedence, the response was that Nero too was the son of Claudius, with Agrippina linking him back to Augustus.

Marcus Junius Silanus, proconsul of Asia whose brother Lucius had been eliminated by her as well, was poisoned for no other reason than that he had been the great-great-grandson of Augustus.

[37][38] Before Nero's consulship in 55, he had forbidden the persecution of a Julius Densus, an equestrian whose partiality for Britannicus had been construed as a crime.

[40] In the account of Tacitus, Agrippina says to Nero:[41] that Britannicus was now of full age, he who was the true and worthy heir of his father's sovereignty, which a son, by mere admission and adoption, was abusing in outrages on his mother.

All that the gods and she herself had taken care of was that her stepson was yet alive; with him she would go to the camp, where on one side should be heard the daughter of Germanicus; on the other, the crippled Burrus and the exile Seneca, claiming, forsooth, with disfigured hand, and a pedant's tongue, the government of the world.Tacitus recounts Nero's numerous attempts to undermine Britannicus' image publicly.

Britannicus, however, not only avoided humiliation but also generated sympathy amongst the guests by singing a poem telling the tale of how he had been cast aside in favour of Nero.

[40] According to Suetonius, Nero moved against Britannicus, employing the same poisoner, Locusta, who had been hired to murder his father, Claudius.

Tacitus' account of the event is that Britannicus was given a hot drink, which was tested by a food taster, and when he asked for it to be cooled, the poison was added to it with the cold water.

[43] Nero claimed to those present that Britannicus was merely experiencing an epileptic seizure and that he had been affected by the condition since childhood.

[46] Britannicus was said to have criticised Nero's singing voice, and referred to his adoptive brother by his original name of Lucius Domitius.

Ominously for Agrippina, Seneca and Burrus did not complain: either they had been bought off or regarded Britannicus' death as inevitable given his relationship with Nero.

[48][25] According to Suetonius, Britannicus was good friends with the future Emperor Titus, whose father, Vespasian, had commanded legions in Britain.

As part of the Flavians' attempts to link themselves with the Julio-Claudians, Titus claimed that he had been seated with Britannicus on the night he was killed.