Having left years between reading the first two books of the Small Change trilogy, which are separated in time by just weeks, I then find on reading the third a few weeks after finishing the second that it is set almost a decade into Walton's alternate timeline where Britain settled with Hitler in 1940 and moved sharply towards fascism. Now the two viewpoint characters are the gay secret police chief Carmichael and his unsuspecting ward Elvira, and the tangled web of coercion and lies which has sustained the British government for many years is stretching to breaking point. It's a simpler book in plot terms - now that Carmichael has become a secret policeman rather than a detective, the plot is about conflicting state security structures rather than solving crime - but I was gripped to the end, knowing what Walton is capable of doing to her viewpoint characters and hoping that it might not happen this time. My only slight cavil is that a personality shared by our timeline demonstrates a crucial heroism at the end which I fear the real-life counterpart might not have. But I also smiled at some familiar names from fandom showing up as characters.
Really excellent stuff, and I recommend the entire trilogy - Farthing, Ha'Penny and Half a Crown - without hesitation.