He probably would have been a hell of a Caligula in the 1937 I, Claudius.

Forgot to mention that years ago I saw The Epic That Never Was, which I think is included on the box set you lent out. There’s a clip of 1930s Williams as Caligula, camp as two tents and about to introduce a newly-appointed senator—then we cut to Williams thirty years later telling an interviewer: “I feel so sorry for that horse. All that build-up and he never got to make his grand entrance.”