For the record, photos of my newly acquired 1984 Lotus Eclair. You can clearly see the works "One Key Release" around the hex head.
I came across this discussion because I too was curious about removing the crankset. I tried turning the hex head to loosen, and after an initial release of stuckness, got only 1 or 2 turns before it hit a wall and wouldn't turn anymore. I guess I was backing out and hit the crank itself. Will try to lube and come back tomorrow. I guess I'll need to put some force into it, yes?