What insight does Pip gain into Wemmicks private life in Charles Dickens's Great Expectations?

In his search for a father throughout the narrative of
Great Expectations, Pip seeks this parentage with Joe, but because
he succumbs to the "rampages" of Mrs. Joe, Joe is unable to fulfill the role, Then in
London, Pip finds some paternal warmth in John Wemmick.  But, Mr. Wemmick leads a dual
life: the one as a clerk with a "post-office mouth" and the other as the devoted son at
Walworth, which is outside London.  Wemmick has chosen to live outside London away from
the grime and corruption.  In the district of Walworth he has created "the castle,"
replete with moat, drawbridge, and cannon, the Stinger, that Wemmick fires for the
delight of Aged Parent.  Behind the fortifications, Wemmick has a miniature farm with a
pig and some fowl.  Then, as they drink punch in a shaded area, Wemmick tells
Pip,

I am my
own engineer, and my own carpenter, and my own plumber, and my own gardener, and my own
Jack of all Trades."

“Well, it's a good thing, you know. It
brushes the Newgate cobwebs away, and pleases the Aged
Parent."

When Pip asks if Mr.
Jaggers likes his property, Wemmick informs him that Mr. Jaggers has never been to
Walworth:

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“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.”

Mr. Wemmick separates
his private live from his public life. The next morning Pip finds his boots cleaned by
the kind Wemmick who is in the garden nodding and smiling at his old father.  However,
as they walk to little Britain and Mr. Jaggers's office, Mr. Wemmick transforms again to
the dry little man with the mere post-office slot of a
mouth:

By
degrees, Wemmick got dryer and harder as we went along, and his mouth tightened into a
post-office again. At last, when we got to his place of business and he pulled out his
key from his coat-collar, he looked as unconscious of his Walworth property as if the
Castle and the drawbridge and the arbour and the lake and the fountain and the Aged, had
all been blown into space together by the last discharge of the
Stinger.

While Pip is amazed
at the duality of Wemmick, he is warmed by his charming dinner at Walworth and his
comfortable stay, a stay that is certainly in contrast to his stays at Uncle
Pumblechook's where he has been treated as much less than a
guest.