From a 2003 Benjamin Cook interview, it’s Nicholas Courtney’s oft repeated and much loved ‘everyone was wearing eyepatches’ anecdote:
Has anything amusing ever happened to you in connection with an eye-patch?
“No, no, no – look, I can’t tell that anecdote again. I’ve told it so many times before. [Buries head in hands] It’s not funny anymore. [Heavy sigh] This is the last time I’ll ever tell it. It was during Inferno, wasn’t it? Yes! And the Brigadier was playing the Brigade Leader. And he was in his office, wasn’t he? And Jon Pertwee, Caroline John and John Levene knocked at the door and came in, and I spin round… and there they all are, wearing eye-patches! They fell about with laughter – but oh no, not me. They couldn’t make me laugh. John cracked up first, Jon Pertwee second, Caroline third, but I kept a straight face. And that is the eye-patch story. Why it’s a legend, I do not know. Are you happy now?”
…I’d have thought last night’s episode was a tribute even without the phone call.