Which Roman emperor was played by Christopher Biggins in the British television series 'I, Claudius'?

Based on Robert Graves' 1934 novel 'I, Claudius' and its sequel, 'Claudius the God', 'I, Claudius' (stylised as I·CLAVDIVS) is a BBC Television series that was released in 1976. The show is set in the early Roman Empire from the year 24 BC to AD 54. Several historical characters feature, including Emperor Nero, played by Christopher Biggins (born 1948).

'I, Claudius' covers the reigns of the first four Emperors of Rome, ending with the appointment of Nero, the fifth Emperor. At the beginning, Emperor Augustus, played by Brian Blessed (born 1936), is trying to find a suitable heir. On his death, his step-son Tiberius, played by George Baker (1931-2001), becomes Emperor. The show continues to follow the historical accessions of the emperors with John Hurt (1940-2017) as Caligula and Derek Jacobi (born 1938) as Claudius, who also narrates the series.

Christopher Biggins was chosen for the role of Nero after starring in an advert for Heineken, in which he played the same Emperor. Nero (37 AD-68 AD) was the fifth and last Roman Emperor of the Julio-Claudian dynasty. He was the adopted son of his grand-uncle, Claudius, and became Emperor in AD 54, after Claudius died.

'I, Claudius' initially received negative press but went on to become a big success. Derek Jacobi and Siân Phillips (born 1933), who played Livia, the wife of Augustus, won Best Actor and Best Actress at the 1977 BAFTAs (British Academy of Film and Television Arts).