PS, the pictures of Cleeve's lathe are impressive though. Thanks for the pointer.
It appears he has, in addition to the screwcutting spindle clutch, a leadscrew dog-clutch. I would love to know what is iniside that square box near the end of the leadscrew. . I am planning to make a dog clutch for my ML7 leadscrew but so far am looking toward the simple ML10 sliding sleeve type, sort of a simplified M Type set up.