Please provide me with a thematic study of "The Duchess and the Jeweller."

The most abiding theme in the story is the way that money corrupts people, making them do things they really should not do. The jeweler, Oliver Bacon, has money, plenty of it, but the one thing he lacks is social respectability. Despite his enormous wealth, high society still looks down on him as an upstart and a parvenu. The Duchess's financial embarrassment provides him with the opportunity he has been waiting for: a chance to gain admittance into the very highest echelons of English society.
The Duchess has social respectability in abundance, but she has little in the way of hard cash thanks to her reckless gambling habit. She turns to Bacon in the hope of easing her somewhat reduced circumstances. In their squalid little arrangement, both Bacon and the Duchess compromise their integrity to gain something they both desperately need.
Arguably, Bacon gets the better of the deal. Although he pays good money for something he knows to be fake, he has shown he has the confidence and the guile to wheedle his way into high society. Once he is there, it is unlikely that he will ever leave. He might very well end up marrying the delectable Diana, which is what he really wants most of all.
It is also likely that the Duchess will continue in her profligate ways, racking up ever greater gambling debts. In doing so, she will become even more indebted to Bacon, who will exert greater control over her life as a result. The suggestion here is that the aristocratic soul is destroyed by money, whereas the likes of Oliver Bacon have already been corrupted to such an extent that their souls are almost completely formed by money. Thus, they have nothing more to lose in the spiritual sense of the term.