It definitely needed two game-masters, because there were a lot of consultations with the GM. We had an open space of three rooms representing the public space of Blandings Castle, plus the porch outside where we had the in-game garden and lake area. Players would go into the kitchen to consult with the GM to go into private areas: people's rooms, the pig sties, the museum and the library. These were represented by a set of envelopes containing slips of paper for various items.
I think we did a fair job as GMs. The one big slip-up turned out to be rather amusing. Robert, playing Lord Emsworth, went to check on his pig early on, but accidentally put the pig card into his pocket. For the next two hours, he and everyone else (including us GMs) thought that the pig had been stolen and were trying to find out who had done it. I think there were plenty of events to go on. The one point I think was disappointing to some players was that their romance plots were never activated -- possibly due to not being seeded by missing characters.
I didn't follow the romance plots too closely, but it was a very amusing mechanic that fit P.G. Wodehouse rather well. Unmarried female characters had instructions that their romance plot would be activated by a certain key word or topic. Compatible men were marked by a symbol on their name tag (a bell, asterisk, etc.). If a compatible man mentioned a certain topic in conversation, the woman would open a sealed slip of paper and hand the matching slip of paper to the man in question. So a drone could suddenly find himself in love with and/or engaged to a woman seemingly randomly -- which is quite in keeping with the Wodehouse tradition.
I think a nice thing about the plots in general was that everything was of similar importance. All the plots were of personal importance to the characters, but none were objectively central. People's reputations were endangered, but there was never any life-or-death issues at stake. No one was biffed through a few people were frisked.
Karen has some pictures of the event on her Flickr account, flickr.com/photos/kindle.