"The Prime Minister" is based on the Marquess of Pombal's life. In this book, William Henry Giles clearly states that he did extensive research for the story, writing to friends in Lisbon who "put at my disposal all the documents they possessed relating to their families' private histories." He could also visit the Porto public library, which he admired. It's worth noting that the novel begins with a description of a sea voyage, which is the theme of the majority of Kingston's subsequent novels. Throughout the book, he employs the narrator's voice, which constantly asserts the veracity of the facts narrated. It is, however, clearly a novel rather than a historical work.