So then I came down with a bad-cold-possibly-the-flu and went off to a farm for three days to help fence a sheep pasture, which is a better life decision than it sounds like, because SHEEPS and FREE-RANGE CHICKENS and BABY DONKEY and RIDING AROUND IN A CART also, like, farm. Yay for little hobby farms that might be something more some day.
Also I was thinking about Rivers of London, and about how I probably wouldn't have had the courage to write Mama Thames the way he did, because of the way she gets close to certain stereotypes that can be dangerous to play with, but also that I'd like to hope that I would still be able to have that kind of diversity in the story, and it occurred to me that probably what I would have done is made the West African lady be the Last Living Newtonian School Wizard instead of the Dangerously Sexual River Goddess-Mother.
And then I started trying to make it work, because, okay, if she's the last survivor of the Folly, then obviously the Nightingale jumped into the Thames sometime in the early 50s and then found himself crawling out with a whole new kind of magic behind him, which is also FUN, but means he wasn't there either when the last of the WWII veterans died or retired or were invalided out. But they needed SOMEBODY who could keep the agreements and responsibilities, at least until the magic had died out enough that it didn't matter. And they couldn't find anybody, except - there's this black woman, friend of Molly's from below stairs, maybe, figured out Lux on her own and then kept wanting to know, and became somebody's Eliza Doolittle project - just curious whether a pig could be taught to sing, not whether it was well done, but a secret apprentice kept him going when there wasn't much else that pulled him out of the fog, and she was good at it, and hungry to learn, and before either of them realized, she'd made mastery.
And probably her teacher took himself out not long after because dude had issues. but that meant that when they needed someone, anyone to hold the Folly - when the last few half-trained survivors of the War put their heads together and sent out a spell to search for anyone who still had Mastery and could be talked into doing the job, probably only a few years after Nightingale went into the River - she was what they got: young West African woman, maybe mid-twenties, worked as a housekeeper most of her life, but inarguably oathbound to the Folly and inarguably a master of Newtonian magics.
Obviously this would not go down well with a great many people, but magic is dying anyway, right? really all they need is a placeholder to keep things from falling apart catastrophically before they wind down, and you couldn't ask a young man from a good family to waste ten years training on something that will be useless in twenty, so why not?
So then it's just her and Molly rattling around the big old place for a long time, and probably without even the police connection to keep them busy.
Of course once it becomes clear that magic isn't dying out for good it's much too late to change their minds and there's nobody else left at all; they do start trying to send her apprentices - those nice young men from good families - but none of them are interested in working hard enough to learn, or at least not working when it's her teaching them, and inevitably they learn that a "real" Folly wizard is still alive, because the Nightingale didn't exactly die, and then they go off to the Court of the Thames to get him to back them up. And when they come back from the River they aren't interested in being wizards at all any more and usually end up moving to Herefordshire.
Until she stumbles on Peter, of course.
I don't have a plot (other than that her relationship with Uncle Thomas Thames would be very very interesting) but I did have an entire night of fever dreams based on it so I'm convinced it would totally work.