Anti-Catholic Sentiment
The Gordon Riots occurred as a backlash against the Papists Act of 1778. This act gave Catholic citizens limited human rights if they promised allegiance to the monarch of the day, but it also gave the Pope theological monarchy of the land. This was a change that was unacceptable to the largely Protestant Londoners, who had experienced a great deal of loss and bloodshed in battles against the Spanish Catholics in their lifetime.
The novel is basically a story of Protestants versus Catholics, a long-standing theme in the history of the British Isles that goes back centuries. It also suggests that Dickens did not approve of this conflict, uniting young lovers on both sides of the conflict together at the end of the book.
Distrust of Politicians
This is a sub-theme of the central theme of the book but is nonetheless something that both this novel and A Tale of Two Cities strongly exhibits. There are two largely "political" figures in the book; the fictionalized real life character, Lord Gordon, and the entirely fictional Sir John Chester. Both men are controversial, full of bluster and largely obnoxious, with Chester seen also to be a bigot and a manipulator. These characters and the qualities they have been attributed by Dickens show the author's own feelings about politicians and the fact that the people should not trust them.
The Need for Penal Reform
Dickens was a vociferous opponent of the penal system of the day, believing it to be antiquated, unjust and that it encouraged the "scum of London" to get out far too quickly and again terrorize the city. He demonstrates this feeling by adding in several characters working in law enforcement, such as a hangman, and showing that they cannot be trusted. The Riots took place several decades before Robert Peel reformed the entire penal system during his time as Prime Minister, in which he overhauled jails, regimented sentences and punishments and also created a Westminster Police Force who became known as Peelers, and later, as Bobbies (an abbreviation of his name). In Dickens' day, the penal system was understaffed and largely ineffective.
Village Life
A large part of the book deals with the day to day goings on in the village of Chigwell; the general comings and goings, villagers involving themselves in the lives of their neighbors, and the unwritten village hierarchy that decides for itself who the "elders" are going to be. In most villages this is the owner of the local inn, and this is the case in this novel too. The villagers are also seen to be protective of each other, for example, Geoffrey Haredale protects Mary Rudge and her son from the unwanted attention of the mysterious stranger who appears to be stalking them.
