Slitherine

I cannot figure out the rule for turning units in place. The rules state that drilled units can turn and continue to move. I've never been able to turn a drilled unit and then move it. And after moving, sometimes I'm allowed to turn a unit and sometimes not. I can't figure the pattern. In one game just now, I had four identical drilled cavalry units, all in command, move the same distance, none of them coming into contact, and 1 was allowed to turn ,and the other three were not. What's the rule?

Admittedly, the explanations are somewhat confusing, even on here: http://fog-pc-wiki.wikispaces.com/Manoeuvring.

The easiest way to think about it is don't turn BEFORE you move, or it gets complicated. Basically, undrilled troops will take a movement point by turning/moving in a direction that isn't their frontal arc. Drilled troops will not. Again to keep it simple when you're making a critical move, if any drilled/undrilled troops advance through their frontal arc, at the end of movement, they can turn to face any direction.

Hope the link and my explanation help.