I thought this one was much more gentle than it first appeared - which was a relief! I am however a little nervous about Mrs A's reaction to the square of nine. "That old chestnut!", she says, "Slope the lines a bit and...". This seems to imply that the lines in the square of nine are not sloped, but I don't see how that can be the case! Have a missed something obvious?
That niggle apart I thought it was an excellent puzzle and had no particular issue with the controversial unch as there isn't really anything else it could be. Perhaps a few words at the very end of the preamble went missing. Thank you very much Mr and Mrs A.