Not a plausible alternate reality. The UK had draconian detention regulations in WWII (Defence Regulation 18B allowed the detention of citizens without habeas c

Not a plausible alternate reality. The UK had draconian detention regulations in WWII (Defence Regulation 18B allowed the detention of citizens without habeas corpus) but even we were weren't daft enough to use it on the entire German-descended citizen population - mainly just our homegrown fascists (and never more than 1000, I think). No mass murders. Obviously.