That's the only one I have been unable to solve.
I've got the victim and the fateful location but it seems to me a copy of the Oxford book (which I don't have) is necessary to find the surname of the commentator. I found the joke on the internet but it doesn't seem to be ascribed to any particular person.
I think the first sentence in the preamble would have been clearer if it had said "elsewhere in the grid" rather than "in the rest of the grid" which to me implies all of the rest of the grid is involved.