By the way, "Portable Ghosts" is about a couple of ghosts who haunt (respectively) a book and (eventually) a laptop computer. Portable ghosts... get it? It is nice to think that Mahy's spirit is just as portable - inhabiting every one of her many great books and leaping out to astonish her readers every time - just as it did while she was still alive.
In case you're interested, I've written a bit more about Margaret Mahy here in this blog. And here is a comic strip I wrote about her. I've written about Gilbert & Sullivan here and there in The Drawing Book, but I don't think any of that stuff is online. Ah well... I'm sure it's only a matter of time!