It was only a sleepless night on Bert’s behalf that enabled us to solve the puzzle. Lying awake desperately trying to think of connections, the penny suddenly dropped. It was then frustrating not being able to write things down to confirm everything. Joyce was oblivious to all of this frantic brain activity and was somewhat shell- shocked when all was revealed (so to speak!) the next morning.

Why we have never sent our completed entries off is sometimes a mystery – the challenge we suppose is in the solution and this certainly was one if those that left us amazed.

Thanks again to Nimrod and Hihoba for the blog.

It was certainly a ‘moment’ to discover that there are four and only four capital letters that lend themselves to each single capital, and then to find out they could be arranged as QUIZ, one of which I was running at the time (somehow I wasn’t alert to it at the setting stage!). The gradual dawning on me is reflected in the saving of this puzzle until the date of IQ 1,2,3,4 arrived.

Individual clue comments/justifications:

1dn (Q)UANTUM: ‘leaves’ is verbal – if you kick about (the letters of) AUTUMN, you ‘leave’ a word meaning ‘the smallest amount’.
7ac PL(U): not much to work with here, but I hoped the clue abbreviations led to the abbreviation of Labour Party.
43ac: IT, usually the minority, whether s/he is doing the catching or the avoiding. Cornish upbringing!
6dn: density is how closely the molecules/atoms are packed in an entity – ‘how close’ seems fair to me.

Finally, as John L says at #7, I can see no ambiguity with QUIZ being the necessary entry below the grid.

Thanks for the great blog and kind comments (Tramp, you flatter me!) on this site and elsewhere, and also to Mark Goodliffe for performing many of the proof solving/editorial duties for this puzzle.

John H

I feel the rubric was unambiguous: “…key event should be named under the grid… The event’s letters are ignored in wordplay…” So QUIZ should be written under the grid.

Thanks to Nimrod – very ingenious – and definitely to Hihoba for sorting everything out so clearly.

I think the original “Henderson Scale” was 1-3 (much too crude) and was unofficially adapted by bloggers to 1-5. I would definitely give this one a 5.

Not only are QUITO, ULAN BATOR, ISLAMABAD and ZAGREB the only capitals to start with Q, U, I & Z respectively, but, as Tramp indicates at Comment 1, no other letter of the alphabet leads to a unique capital city – so I just wrote QUIZ below the grid.

The wordplay for 32a NEMN (via ONE MAN – never heard of it) took an age; and I’m still not cpmpletely convinced by the wordplay for 6d DENY. (As for “leaves” in the clue for 1d, Hihoba’s comment “Couldn’t find any reason for this word.” seems apt.)

But a very impressive grid construction. Thanks, Nimrod.

And I failed to make the “fascinating discovery” that they are the only word capitals that start with those letters. I’ll be amazing all my friends with my new-found knowledge!

I wrote CAPITAL QUIZ under the grid but I’m not sure that was right.

Nimrod sets quizzes. I presume on the evening in question he made the fascinating discovery that the only countries to have unique initial letters in their capital city’s names are Ecuador, Mongolia, Pakistan and Croatioa; Q, U, I and Z, respectively. I find this discovery amazing — as Nimrod did.

I spotted in the grid quite early on a few countries so tried to work out where some others could go. I then spotted the unclued letters Q, U, I and Z were in the corners of the grid. I made the connection with the capital cities and then I had a great penny-dropping moment when I realised he’d hidden all the capital cities diagionally in the grid.

I think it’s the work of a genius!