Honestly, I always get distracted by the visceral, grimy details more than the grand setting itself. 'London' in these novels isn't just a backdrop; it's a character that sweats and breathes and decays. Think about the pervasive dampness in a Sherlock Holmes story—the fog isn't atmosphere, it's a plot device that hides a killer's approach. The cobblestones aren't picturesque; they're slick with something you'd rather not identify. For me, the main setting is the network of contrasting spaces: the claustrophobic, gaslit interiors of a drawing room where social ruin is plotted, versus the vast, indifferent sprawl of the Thames, carrying all secrets eventually to the sea. The plot often lives in the tension between these spaces, the performative gentility of Mayfair and the desperate, seething energy of the docks or Whitechapel.
That geographic and social chasm is where the real drama unfolds. A character's journey from one sphere to another usually drives the central conflict—whether it's a secret from the colonies disrupting a Belgravia ball, or a detective navigating both worlds to find the truth. The city's architecture, its literal layering of Roman, medieval, and modern, mirrors the layered secrets the plot unpicks. So while you could say 'Victorian London' or 'post-war London,' the core setting feels more like 'the labyrinth,' a physical and moral maze the characters must navigate, where the next turning could lead to opulence or utter squalor.