Okay so like I had a random idea for an AU (inspired a bit by @joyful-downer 's drawing requests, simply because one involves Uncle Jack and Horus-), so I'm gonna ramble here a bit.
AU Where Margaret was never killed. Jack was able to successfully hide her from the German soldiers and the trains left.
Now Jack has to hide her, but the Bobbies have been combing the town to make sure no other children have been left behind. Frequent checks are done on all the houses, and on one of these visits, a certain Constable Horus Hunt visits Uncle Jack to do a routine inspection.
And Horus finds Margaret.
So Jack has to plead with Horus not to tell anyone, that if they knew of her, they would take her away from him, or even kill her.
Not only does he keep quiet, but he also helps take care of the little girl. He knows that food is hard to come by with the war rations and everything, so he visits often and brings them food and other supplies since Jack is scared to leave her alone at home. Horus also makes sure no other bobbies visit Jack, ensuring them that he himself has ensured that Jack is clean and isn't hiding anything, and no one bats an eye.
Of course, Horus quickly grows attached to the both of them. He wants to protect both of them and becomes a sort of secondary parental figure for Margaret. Being a child in a childless town and having to remain hidden hasn't been easy for her, and he knows that. He brings her toys he finds in town and will play piano for the both of them and tell her stories to keep her happy. He also helps with homeschooling her, since Jack already has so much on his plate.
The visits had started off short, with Horus just stopping by for a few minutes to drop off supplies and food and say hello. Then, the visits became longer, with Horus spending more time with both and minutes became hours, until he would even stay overnight with the Worthings.
Margaret always looks forward to Horus's visits. Jack insists he tries to pay Horus back somehow, yet the constable refuses every time. Their company is payment enough for him. Horus finally feels as if he has a purpose in watching over Jack and Margaret, which is something he has yearned for his whole life. Horus didn't grow up in a loving family, and he never had anyone he cared for deeply. He was an only child with an emotionally distant father, and he never had friends growing up. Now, he has Jack and Margaret to look after and care for, and he couldn't be happier.