In Nightfall One, Asimov says this about a radio adaptation of C-Chute:
Once television came in, I found that voice, and matched the face to it, and that looked like Mullen. … I have carefully refrained from learning the actor’s real name. I want him to remain Mullen.
There’s a recording of the dramatisation, which doesn’t have credits. They might have been removed by the uploader, or maybe weren’t there to start with.
Do we know who played Mullen in C-Chute?