Have you ever tried to work out what it is about his photos of women that makes (most of them) instantly recognizable as Newtons?
It's noticeable that he very often shoots from below eye-line, as though he always used a waist-level finder (but the men often from above)... and that typically the subject looks as though she is contemptuous of the photo(grapher). Maybe he was sufficiently confident in his status that he didn't need to create images of women who looked as though they were flirting with him... which many photographers seem to need. Which is very different to the runway model affectation of models looking as though their cat was run over by the taxi on the way to the show...
That's something I've wondered about too.
My feeling is that he's very careful with model selection, and then uses hard lighting (and equally hard makeup) - often on contrasty or very dark clothing, anyway - and that it's the repeated combination of these into formula that gives his look its look.
There's something that I think spells lesbian about his models, even though they may well not be. He eschews the easy smile route.
About having women look as if they are flirting with the snapper: I think it's more having them flirt with the viewer. I don't think I tended to make the mistake of thinking there was the slightest thing personal about shooting models, in the sense of expressions they give or you coax, but there certainly was a lot of personal input that led to easy working. That's not always the case with people you've never used before; it's also a good reason for doing as much research as you can on their track record just to get an idea of their apparent 'routine' which, if they work a lot, tends to show up over a collection of shoots.
On the other hand, first-shoots can also do quite the opposite, and show a side to the model you didn't know was there, just because the pix you'd seen came from snappers without the same sensibilities that you put into play which, in turn, affect the model. My one and only muse hit the G spot on her very first test with me: I got the best shots I'd ever made up to that moment the evening she showed up. Point of no return, and also the start of some little envy/dislike from some other girls in the same model agency because she got most of the work they wanted.
If there's a problem with using one model too often, its that you both fall into the easy trap of repetition. This can save your mutual bacon in some situations, but also lets you down a bit... Too much safety can be a hindrance.
Referring once more to Bailey: I think it was Penelope Tree who said "Bailey hates surprises," but it could have been any other of the long-term muses.
Didn't Donovan say that Newton didn't print his own work? Perhaps as much is owed stylistically to a long-term printer's input as to Newton's!