When their serial publications were completed at the end of the year, Ainsworth began writing Old St. Paul's, A Tale of the Plague and the Fire.
[3] The story of Old St. Paul's is spread over six books that range between April 1665 and September 1666 and details the events of the grocer Stephen Bloundel's life.
Part of the story deals with the pursuit of Amabel, Bloundel's daughter, by Leonard Holt, the grocer's apprentice, while she in turn pursues Maurice Wyvil.
He is similar to characters in at least two of Ainsworth's other novels, who give prophecies about the future: Elizabeth Orton from Guy Fawkes and Gunnora Braose from The Tower of London.
Other incidents of social decay involve people ignoring helping their fellow man or, as the characters Malmaynes and Chowles do, simply murdering and robbing the sick.
The standards of life are revealed, with the sick killed by those supposed to help; religion turned upside down, and death and destruction celebrated.
[13] In an advertisement for the novel on 30 November 1841, Ainsworth admitted that portions of the tale were "founded on a narrative, which I have followed pretty closely in most of its details, contained in a very rare little volume, entitled ' Preparations against the Plague, both of Soul and Body' , the authorship of which I have no hesitation in assigning to DEFOE.
[16] R. H. Horne, in A New Spirit of the Age claimed that Old St. Paul's is a copy of Defoe's Journal of the Plague Year in addition to being "generally dull, except when it is revolting".
The Bell's Life of London wrote, "Although the horrors of the Plague and Fire have already been described by various writers, and especially by Defoe, Mr. Ainsworth has in these volumes clothed those events in a manner the most exciting.
"[19] A review in The Atlas states, "Two of the most appalling events in the history of London have been drawn into the work before us [...] and treated in Mr. Ainsworth's usual graphic style.
"[19] The Observer claims, We are glad to meet Mr. Ainsworth again in the region of historical romance, a department of literature in which he has already distinguished himself above every author of the day.
"[21] A review by The Court Journal claims, "In this tale of the Plague and the Fire [...] we recognise all the excellences which have gained for Mr. Ainsworth so high a name on the scroll of historical literature.
There is the same centralization of interest; few marked personages; a plot not too transparent, but of great simplicity; easy power, and most natural pathos in the more tragic portions; characteristic dialogue; and over all, a lucid style of expression.
"[21] In 1934, Malcolm Elwin argues, "several of his novels – particularly Tower of London and Old St. Paul's, in spite of the absurd antics of the hero of the latter – have undoubtedly the quality of durability.
"[23] George Worth, in 1972, describes the structure of the novel: "the rationale and the coherence of each part are clearly and persuasively worked out, and the contribution of each to the whole narrative requires no defense.
It is a 'disaster story' worthy of Hollywood, where an all-star cast is introduced merely to be decimated by fire, flood, earthquake, shipwreck, alien invasion, or act of God.