Best impersonators? Theatre or Screen actors?

Question

Montgomery and Churchill got actors to impersonate them for security reasons.
But today, which acting discipline is best for such a role?
Are Theatre actors over expressive (so they can be seen from the back of the theatre)?
Are TV and movie actors too relaxed (they only need to keep in character for a few minutes before "CUT")?
Which is best at impersonating a celebrity for hours at a time?

Answer 1

Interesting question. I'm inclined to go with theatre actors for two reasons. First, they are taught the discipline of keep the performance "fresh" while being consistent in characterization. Second, they are used to responding to live audiences and "thinking on their feet" as they say... something which an impersonator would need to do to be convincing in his/her role.

Answer 2

I think I'd go with an actor trained in improvisation for such an unusual gig, and you'll find those in both live theatre and in TV (think Whose Line is it Anyway? or even Saturday Night Live/MadTV, many of whose actors come from improv troupes like the Groundlings and Second City) Improv is the ultimate in "thinking on your feet" and sustaining character in any situation. Improv masters are also trained to convey character quickly and accurately, since they don't usually have much time to get their point across. And they often have a stock of impersonations they're already skilled at.