That C.B. Style

So, I was under the impression that the whole riding boots, jodhpurs, cap/beret, look was DeMille's. I was aided in this assumption by lines from DeMille bios stating things like, "In his trademark leather puttees and jodhpurs..." But now, looking at this picture, it seems that either 1)everyone who worked on a movie set wore this combo, this kind of movie-making uniform, if you will, 2)DeMille liked it so much he demanded anyone who worked with him wear the same thing, which seems unlikely because then he wouldn't stand out or 3) everyone just wanted to be like C.B.

Of course, other photos of other directors...

...lend support to the beret/cap being, at the very least, a part of some required director's uniform. But did it come from DeMille or just that everyone on a movie set in the twenties wore them and he was the only one remembered for it? Were you given a dress code violation for not wearing one, or for wearing a baseball cap or fedora instead? And, finally, did the studios provide them or did you have to buy your own?

So many questions, so few answers. All I know is, when I become a big time director, I'm bringing back the Fellini/Frankenheimer look. The beret thing's been so done, you know? Besides, all these years later and still no one does it better than DeMille.