Easterhay said:
And isn't the way Alec Guinnes paused before replying to the question "How did my father die?" just perfect? It's as though Lucas had told him the backstory on the quiet.
Absolutely. George must've had some small inkling about what to do with Luke's dad (not sure if Anakin came at that time. It was almost Alec had seen Sith, even though he (obviously) didn't.