'The Third Man' was actually a Carol Reed film. Welles claimed he did not give Reed any advice but it sure looks like it.
I know, but he permeates the film, in fact, he doesn't even appear until a good 40+ minutes into it, he steals the movie before even being revealed, by a trick of light.
As for Carol Reed, did you know, his daughter is in Dr. Strangelove? She is the leggy girl in the bikini in bed with George C. Scott.