Pip comes of age (turns 21) and is called to Mr. Jaggers' office. Expecting to be told the name of his patron, Pip is surprised when Mr. Jaggers points out that Pip is deeply in debt and gives him a five hundred pound bank note. Pip will now receive this annual sum to manage his own expenses rather than drawing allowances from Wemmick. He tells Pip that his patron's identity is still a secret.
The new arrangement gives Pip more independence, but it's unclear whether he has developed enough judgment to use that independence responsibly.
In the outer office, Pip privately proposes to Wemmick that Pip invest money in Herbert's career. Wemmick objects vehemently to Pip's proposal, telling Pip never to invest "portable property" in a friend. When questioned, he tells Pip this is his "opinion in this office." Pip tells Wemmick he is going to visit him at Walworth to hear Wemmick's Walworth opinion.
Pip's proposal is extremely generous. Wemmick upholds his professional reputation by giving him a business-minded opinion at the office. To get Wemmick's advice as a friend, Pip must go to Walworth.