I, Claudius (TV series)

"The director and producer ... [Herbert Wise and Martin Lisemore] went on to do I, Claudius. [...] Their first idea was to have two different actors playing Claudius, one young, one old. But when Charlton Heston and Ronnie Barker turned down playing the old Claudius, they thought, "Why not have a single actor who ages instead?" Well, that's exactly what I'd done in Man of Straw, so their next thought was, "Derek could do it.""