Pip first visits Wemmick's house in Chapter 25. Though Pip sees Wemmick as a strict, all-business worker in Jaggers's office, Pip sees an entirely different side of Wemmick when he visits Wemmick's house at Walworth.
When the two arrive at Wemmick's house, Pip observes the house to be a "little wooden cottage in the midst of plots of garden, and the top of it was cut out and painted like a battery mounted with guns."
Immediately, readers understand the pride Wemmick has in his home; he says, "My own doing. Looks pretty, don't it?" and then proceeds to tell Pip about his flagstaff, bridge, animals, and vegetable garden. Next, Pip meets Wemmick's "aged parent," who is also proud of the care Wemmick takes both of him and of the home.
When Pip questions Wemmick about Jaggers's reaction to Wemmick's house, Wemmick says,
Never heard of it. Never seen the Aged. Never heard of him. No, the office is one thing, and private life is another. When I go into the office, I leave the castle behind me, and when I come into the castle, I leave the office behind me. If it's not in any way disagreeable to you, you'll ablige me by doing the same. I don't wish it professionally spoken about.
Obviously, Pip realizes that Wemmick is not as one-dimensional as Pip had thought. He is a caring man who loves his home and loves his father, and does his job because it is simply that--a job.
Wemmick is clearly a dual personality. He is "wooden" at the office, having "a post-office mouth" that merely takes in the information, sorting it, and sending out what is necessary. In many ways, Wemmick is as coldly business-like as his employer, Mr. Jaggers. But, after he takes a liking to Pip--perhaps from Pip's unpretentious shaking of his hand and good manners toward him--Wemmick invites Pip to come home with him.
What a surprise the charming garden, miniature castle with moat and canon are to Pip who has believed that Wemmick has had little real personality. He is also surprise to hear that Wemmick is a "Jack of all Trades" and how Wemmick's face softens as he speaks lovingly to his old father, the "Aged P." With fondness Wemmick lights the canon at night for his deaf father who is able to hear, at least, its boom. All in all, Pip spends a delightful evening at Wemmick's home and awakens to hear Wemmick solicitously polishing his boots. But, as they walk back to the office in the morning,
By degrees,Wemmick got dryer [sic] and harder as we went along, and his mouth tightened into a post-office again.
One of the most lovable characters we come across in Dickens' "Great Expectations" is Wemmick the clerk in Jaggers' office. Initially, Dickens caricatures him in Ch 21 as a very formal businesslike man with a "postoffice of a mouth that he had a mechanical appearance of smiling."
We tend to believe that he is totally incapable of any emotional warmth or affection. However, Dickens surprises us by revealing to us the genuinely human and humane side to Wemmick's personality in Ch. 25 and 26 when Pip visits him at his "castle" in Walworth: more than the pride in owning a house of his own it is obvious that he adores his "aged parent" and showers him with a lot of attention and love.
Wemmick's 'split personality' is clearly revealed in these lines when Pip asks him whether Jaggers knows about his "castle" and his "aged parent,"
No; the office is one thing, and private life is another. When I go into the office, I leave the Castle behind me, and when I come into the Castle, I leave the office behind me