But still, even phoning it in for the paycheck he's that good of an actor to carry some major gravitas. They did have Peter Cushing as Grand Moff Tarkin too so Alec Guinness wasn't the only well known actor in it.
Exactly, those two great actors were the only famous and recognized talents in the whole movie. Rest were "kids", mostly unknown actors. Harrison Ford was carpenter and background actor prior to Star Wars...
