He wasn't their first choice, not by a long shot. They wanted someone with movie-star clout, and they had their eye on Charlton Heston. But Derek Jacobi, by his own admission, ''charmed the ass off'' the producers of I, Claudius and walked away with the plum title role of the limping, twitching, stuttering Roman. That was 17 years ago, and the memorable performance and the series itself are still considered a high point in TV historical drama.
Since then, Sir Derek (he was knighted last year) has worked steadily on stage but has appeared only occasionally in films and even more rarely on television. ''There were no more stuttering-emperor parts around,'' says the blond, London-born actor, 56, sitting in the lounge of a Pasadena hotel where he has come to promote Cadfael, the current four-part Mystery! series based on the popular historical whodunits of Ellis Peters.
In Cadfael, Jacobi once again dons robe and sandals, this time playing a 12th-century monk who is also a sleuth. The part fits Jacobi well both he and Brother Cadfael share a passion for gardening and a contentment with solitude and he's happy TV audiences won't think he's professionally dead. Which is patently untrue. He won a 1985 Tony Award for his starring role in Much Ado About Nothing and was recently appointed director of England's Chichester Festival Theatre. He appeared in Kenneth Branagh's Henry V Dead Again, and continues to field the occasional Hollywood agent's call (he was seriously considered for the role of Hannibal Lecter in The Silence of the Lambs).
''I'm a jobbing actor,'' he says. Still, his Claudian afflictions left unexpected scars. ''It's remarkable,'' he enunciates clearly, ''how many people thought that I stuttered and was one of those lucky actors who found a part that fitted my disabilities!''