Much of this scene is devoted to providing more of Lord M.'s personal history, explaining how he ended up in a position for which he seems temperamentally unsuited. It turns out that he never expected to become the Earl of Belpher, and was planning to spend his life farming. Forced by duty into a life he didn't want, his former farming ambitions are now channeled into his rose garden. Desiring only a quiet life, he finds himself cowed by familial obligations into doing things he doesn't want to do, like forbidding Maud from marrying who she wants. By stepping out with Billie, Lord M. is acting in his own interests for probably the first time in years. And it is Billie who provides him with the information that George is, foremost, a good person and is also a rich man. As the scene closes out, we know that there's going to be quite an upheaval at Belpher shortly, between the news of Reggie's marriage and Lord M.'s arrival with Billie.
The scene between Keggs and Albert is instructive as the boy is humbled by Keggs' successful manipulator. Albert must acknowledge his inferiority as as a schemer; he is merely a disciple at the feet of the master, as it were. We also see Keggs' skill at manipulating Lord Percy to get the outcome he wants. Really, Keggs is like a slightly evil Jeeves. The upshot of all this is that George is invited to the Belpher dinner party where, with the presence of all of our major characters, we can but assume that there will be some sort of confrontation.