The Curve of the Earth by Simon Morden
WELCOME TO THE METROZONE
Post-apocalyptic London, full of street gangs and homeless refugees. A dangerous city needs an equally dangerous saviour.
Step forward Samuil Petrovitch, a genius with extensive cybernetic replacements, a built-in AI with god-like capabilities and a full armoury of Russian swear words. He's dragged the city back from the brink more than once - and made a few enemies on the way.
So when his adopted daughter Lucy goes missing in Alaska, he has some clue who's responsible and why. It never occurs to him that guessing wrong could tip the delicate balance of nuclear-armed nations. This time it's not just a city that needs saving: it's the whole world.