Yes, Christopher Plummer's accent and antics are, to the the least of it, peculiar, but trying to see this as a historically accurate epic seems to be missing the point. The original play was by Peter Shaffer - he of Amadeus and Equus, and this film follows the same themes - the conflict and tension between between (according to interpretation) real and apparent power, or between ability and genius. The tension between Atahualpa and Pisarro is along the same lines as between Mozart and Salieri, or the Boy and the Psychiatrist. One has the trappings of power and success, but who really has the raw power? Seeing it as a historical epic is a mistake - just as "Becket" is a very modern take on a different battle of wills.