I even toyed around in my head with the idea that the Imperium Romanum didn’t fall outright – provinces broke away when it focused more on issues with the Turks, Persians, and Saracens, sure, so that’s something to consider. Though, as for advancements I’m not quite sure how far scientifically I’m comfortable with given my interest here is very much in the WW1/WW2 spectrum. Y’know. Biplanes, bolt-action rifles, tanks, and the whole shebang.

That’s not even taking into account that the capital of the United Kingdom is probably still Camelot.