I guess if I spent, maybe, ten seconds thinking about my question I would have thought about Patrick McGoohan. Actually, while I was typing the question your boy J.C. came to mind.
Oh dear..I forgot about him!!
Yes, Nick Colasanto (Coach from Cheers) became ill during the filming of Etude and JC and Peter took over the directing duties. And he also helped Peter out with Blueprint For Murder, along with Steven Spielberg, on some of the camera angles and set up shots.