Charles Dickens
Famous author Charles Dickens, who pops up occasionally in the novel, is symbolic of literary royalty and the way that authors are treated as celebrities.
The courtroom
The courtroom that the "Tichborne Trial" occurs in is symbolic of the order, norms, and values that make a society function. Without a vibrant court system, the criminals would rule the roost. Any society that functions well needs a well-functioning court system.
Books
Books, as the entertainment of the time the novel was set in, are symbolic of the quest for knowledge that many undertake and a portal to a different world. Books are tools, and they are portals to a different world; the characters in Victorian England use them as such.
Doing uncomfortable things
A frequent motif in the novel is doing uncomfortable things. Throughout the novel, characters have to do things they aren't comfortable with. For example, towards the end of Ainsworth's life, Touchet grows increasingly uncomfortable with the prospect of being a caretaker for Ainsworth. Additionally, Andrew Bogle is frequently uncomfortable with his involvement in the trial, reflecting the necessities of the time.
Doing what is right
The novel is an allegory for doing what is right. Despite dealing with uncomfortable things, each of the characters in the novel—especially Touchet and Bogle—do what is right. And they are rewarded for it, showing the importance of standing up for what you believe in and doing what is right.
