Peter Clark is (mainly) a scholar of British towns and cities. This is why he came to study clubs and societies; whose emergence/existence is in fact a function of density. An urban phenomenon.
They have their root in medieval fraternities, protestant sects, and guilds. Spreading from London, they were made possible by the especially favourable economic, cultural, and societal conditions in early modern Britain. Conditions that were not met in Germany, France, or Italy - especially due to governmental repression. Thus Clark argues that limited government and free press are also a necessary condition. The latter existed in Britain from the 1690's on when censorship was abandoned.
He relates his narrative to the arguments in the landmark study from Putnam (1993) on civic societies in Italy.
In the conclusion he briefly covers the timespan beyond the scope of the book until the 20th century.