Where is the back story?

Hi, I cannot help but wonder what " true sequence of things" as mentioned in the explanatory note of the first edition November, 1891 occurred to inspire this artistic rendering of "the shaded side of a well known catastrophe" as described in the preface to the fifth and later editions? Upon whom was the fictional Tess modeled? Did Hardy ever reveal the source of his inspiration for this novel or the murder and execution which inspired this sad tale? Does anyone know who the prototype for Tess was and what similarities she may have had to Hardy's fictional Tess?

1856, On August 9 he witnessed the execution of Martha Brown for the murder of her husband, "he stood close by the gallows", "and contributed to the story and final scene of "Tess of the d'Urbervilles", from "A Hardy Companion" Sheesh, I have to answer my own questions, what a lame website!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!