Found this link tucked away in one of the other blokes blogs. This is an old MCC coaching manual from 1952, there's some brilliant stuff in here including some images of Arthur Mailey and Clarrie Grimmett.
The Big Leg Break news
Yep, still persevering with this and now able to get it up over 22 yards with a degree of promising accuracy. The subtleties of the wrist position are flummoxing me at the minute with many of the balls going straight or turning into wrong uns. It seems achievable but more time is required. But I am getting there, when it comes good it is unbelievably good.