By the way, Castle, like Harry Secombe, got a Tony nomination for his role. Interestingly, when the musical got revived by the Chichester Festival 30 years later, with Secombe re-creating his starring role, Castle also appeared in the production, though this time as Sam's father, Tony Weller. (Secombe became great friends with Castle, and his graciousness show at the end, in his exchange with Ed Sullivan.)
Anyway, here's the performance. As I mentioned previously, Pickwick has been mistaken for a political candidate during a local election and is impressed to make a speech. Totally out of his depth, his valet first gives him some advice. Some of the dialogue has been changed so as not to confuse the viewing audience. Instead of calling out, "We want Slumkey," the public calls for Pickwick.