It is extremely clever how Dickens uses the presentation of London to undercut the sense of Pip's excitement and enthusiasm as he goes there to start his life with his great expectations. Barnard's Inn is one of those ways in which setting is powerfully used to indicate the way in which Pip's removal from his home in the marshes actually exposes him to a darker, more sordid way of life that implicitly associates wealth with darkness and corruption. Note how Barnard's Inn is first presented. Having assumed Barnard's Inn to be a kind of grand hotel, Pip is rather shocked to see where he will be living:
Whereas I now found Barnard to be a disembodied spirit, or a fiction, and his inn the dingiest collection of shabby buildings ever squeezed together in a rank corner as a club for Tom-cats.
The impression is not helped by the description of the way in which he and Wemmick are "disgorged" through a passage into the central square, as if they are being vomited out of the belly of some giant beast. Words such as "dingiest" and "shabby" serve to indicate that Barnard's Inn is not the kind of grand accommodation that Pip had been led to believe. Its description plays a key role in matching setting with the kind of corruption and decadence that will come to be such a feature of Pip's character as Dickens causes us to question the value of "great expectations."