Symbolism, Imagery, Allegory
This isn't the chipper London of the postcards—life is decidedly not composed of tea parties and orderly flower gardens and bobbies on bicycles.
Instead, this is the grim city of Dickens—grimy alleyways, dark corners, and a population that seems to have been born wearing wool overcoats and unsmiling expressions:
He would be aware of the great field of lamps of a nocturnal city; then of the figure of a man walking swiftly; then of a child running from the doctor's; and then these met, and that human Juggernaut trod the child down and passed on regardless of her screams. (2.13)
And rather than taking place in only one part of the city, Stevenson’s novel is set in many different areas of London, each meant to reflect the character of its denizens. Soho, where Mr. Hyde lives, is described as being dark and dingy—which, last time we checked, tends to go quite well with people who ooze evil out of their pores. But the entire city is painted in dull and sinister colors, which helps give the novel its evil-laden atmosphere.