However, this is an excellent analysis of a clever puzzle, so many thanks for that. I have posted it to Savoynet, for all the other G&S nuts worldwide to admire.

I’m bemused by the video link, though. Clearly the voice of Martyn Green (from the 1950′s) as Ko-Ko, but it doesn’t look like him…

I found the clues to be well worth solving in their own right, irrespective of their role in revealing the puzzle’s theme, which isn’t always the case with themed puzzles.

I am not terribly familiar with The Mikado, and indeed did not know that the expression “short sharp shock” had been immortalised by it. Once I’d sorted out the perimeter, however, I was pretty sure that G & S would provide the source of the allusion to be highlighted in the grid and turned to Google with that it mind.

Obvious though the blacking out of the one remaining cell now seems, I actually filled it with a letter “b”, to suggest the alliteration of “big, black block”, mirroring that of “cheap and chippy chopper”. So, Nutmeg, you had the last laugh on me this time!

Incidentally, I too found that the NW corner fell into place last of all. And thanks to Hi of hihoba for the explanation of “anticipation”, which I hadn’t fathomed depsite having tracked down the full quotation.

As for Nutmeg’s claim that her anagram of the perimeter’s unchecked letters would be “unhelpful”, I would maintain that the reference to the teahouse hints at Japan and might thus bring images of Mikados more readily to mind.

Unlike Ken, the SW was my last quadrant – first was NW and some of NE, enough to make the leap to SHORT SHARP SHOCK, followed by the rest of the perimeter before too long. And I too stalled a while on CHEAP AND at 12d (which then seemed a prime candidate for being part of the highlighting, together with CHOPPER and its trailing blank).

So, thanks Nutmeg for a stiff workout, and of course Ken for the blog.