RP English wasn't always used for Romans in Hollywood. But given that you're speaking English, not Latin, demanding "accuracy" is a category mistake. It's a mat

RP English wasn't always used for Romans in Hollywood. But given that you're speaking English, not Latin, demanding "accuracy" is a category mistake. It's a matter of analogy: which English dialect today is most fitting, by analogy? RP English has a certain perception in the US, but is it really the best accent in our times? The British Empire is gone, and did not rule the US. The American Empire, though hurtling fast toward extinction, is a sensible analogue. So some variety of American English seems fitting, and in general, an English language American movie will need to translate into American linguistic categories. For example, among Romans, you can vary dialects based on social class, ethnic origin, and so on. But that's if you want analogical accuracy, and that kind of accuracy can work well when the subject matter of Rome is used as an occasion to critique our society.