"London’s topographical mysteries"

Unlike gridplan cities, such as New York, where streets and buildings are numbered consecutively, London has many quirks when it comes to house numbers. Because of the city's long history and rapid bursts of growth, it is common for buildings with consecutive numbers to be far apart from each other. Conrad makes a joke of this, implying that the houses have wandered off from where they were supposed to be. The fact that the unnamed embassy is located in Chesham Square invites readers to connect it with Russia (the real-life Russian Embassy was in Chesham Place).