Derek Jacobi (Claudius) is the only cast member to appear in all thirteen episodes of the series. In second place are George Baker (Tiberius) and Margaret Tyzack (Antonia), who each appear in nine episodes.
An Alexander Korda version was abandoned back in 1937. Directed by Josef von Sternberg, it starred Charles Laughton in the title role alongside Mrs. Korda, Merle Oberon. A car crash involving Oberon was the main reason cited for the cancellation, but sources say it was a troublesome shoot, with Laughton the main source of the problem.
The series was filmed over a period of six months in a BBC studio. Charlton Heston was one consideration for the title role, but because of the extent of the shoot, and Heston's U.S. residency, the idea was abandoned.
The final installment, "Old King Log", contains a pun on the names of both the Screenwriter and the Author of the "Claudius" novels. Before his vision in the Senate, where he sees the ghosts of his past, Claudius mysteriously declares "The man who dwells by the pool, shall open graves, and the dead will live again." This plays on Jack Pulman, the Screenwriter, and Robert Graves, the Author.
Derek Jacobi is only a year younger than Brian Blessed in real-life, Claudius was fifty-three years younger than his great-uncle Augustus. Similarly, Sir John Hurt (Caligula) was only fourteen months younger than Jacobi, whereas Caligula was twenty-two years younger than his uncle, and successor Claudius.
George Baker, who was in his early forties, went on a regiment of diet and exercise, so he could realistically play a young Tiberius. He managed to equal the weight he used to have when he was twenty-four. His tiredness and exhaustion from working out so much, and eating so little, actually made it easier for him to play an often frustrated and bitter character prone to mood swings.
Sir John Hurt (Caligula) plays the great-grandson of Siân Phillips (Livia), who is only six and a half years older than him. In reality, Livia was already sixty-nine years old when Caligula was born in 12 A.D.
When Derek Jacobi was first offered the role of Claudius, he mistakenly believed that he was being considered for the character of the same name from "Hamlet", and opined that he was too young. He eventually played King Claudius of Denmark in Hamlet (1996).
Brian Blessed originally auditioned for the role of Tiberius, but was eventually persuaded to play Augustus instead. He recounted some of Director Herbert Wise's key pieces of advice on how to play Augustus. Wise told Blessed that he should "be as you are, full of flannel", and that he should always play Augustus as an ordinary person, because the reactions of those around him would make him the Emperor.
Sir John Hurt revealed that he declined the role of Caligula when it was first offered to him. Because of the time-span of the production, the fact that Derek Jacobi would be the only cast member to appear in every episode, and the subsequent commitments of the other cast members. It was decided that rather than the customary "wrap party" at the end of the series, there would be a special pre-production party instead, to give the entire cast and crew the chance to meet. Hurt explained that Herbert Wise deliberately invited him to attend the party, hoping he would reconsider, and that he was so impressed on meeting the cast and crew, that he immediately reversed his decision, and took the part.
The miniseries was made at a relatively low cost of sixty thousand pounds for an hour of broadcast material, in a series that had a total running time of six hundred fifty minutes. Considering pound sterling inflation, the entire show would have cost nearly four million pounds in 2013.
Peter O'Toole, who was Sian Philips' husband at the time, reassured the cast at an early showing that the audience would love it, even if the critics didn't. Sian recalled that he found the reviews of the original books which were similar to the first reviews on the television series.