On either side, Thalia saw the tapering stalks of the Museum of Cybernetics, each structure rising at least a hundred metres into the air, each surmounted by a smooth blue-grey sphere, each sphere marked with a symbol from the hallowed history of information processing. There was the ampersand, which had once symbolised a primitive form of abstraction. There was an ever-tumbling hourglass, still the universal symbol for an active computational process. There was the apple with a chunk missing, which (so Thalia had been led to believe) commemorated the suicidal poisoning of the info-theorist Turing himself.
The Prefects are the Demarchist police force; this is a satisfying whodunnit set in the Revelation Space universe, tying neatly into the established storyline.