The preamble had a very long series of steps: misprints leading to “hints” leading to “questions” leading to “elements” leading to “another message” which then had be applied to the grid. It all seemed very confusing to start with, but the first step was clear enough: “Most clues contain a misprint of one letter in the definition.”

It took me about four hours to fill the grid, with some very tricky misprints to find.

19 across “Perhaps referring to stroke in eighty year old, retired—ultimately monoplegia’s assumed” yielded OARY (all letters being checked, so no doubt about it), but I fell into a trap when I spotted that “eighty” ⇒ R. In fact the misprint was “eighty” for “eights”, and the wordplay was “year” ⇒ YR “old” ⇒ O, reversed around “ultimately monoplegia” ⇒ A.

46 across “Pretence one found in king and queen?” looked like it had the wordplay “one” ⇒ I in “king and queen?” ⇒ MEN yielding MIEN, but where was the misprint? Perhaps “pretence” for “pretense”, but I wasn’t sure I could justify “pretense” ⇒ MIEN from Chambers, which gives “pretense … show or semblance” and “mien … air or look, manner, bearing”. Are these close enough?

28 down “Yankee hosted by queen—Earl shed some tears for her” took me a long time. The wordplay was “yankee” ⇒ Y in “queen” ⇒ RANEE from which “Earl” ⇒ E has been removed. The misprint was “tears” for “years”, and the definition was “some years for her [i.e. queen]” ⇒ RAYNE.

The clues without misprints seemed in some cases to be rather oddly worded, with imprecise definitions or extraneous words, as if they had been written under rather severe constraints.

The corrected misprints yielded two “hints for deriving two versions of a question from the remaining clues”: DOT ONE’S ‘I’S AND CROSS ONE’S ‘T’S in the across clues, and IDDY-UMPTY in the down clues. Chambers: “iddy-umpty n Morse code. [From a phrase used in India to teach morse to the native troops].”

Interpreting I as a dot, and T as a dash, the remaining clues could be treated as Morse code letters: this yielded MUST IT BE? and MUSS ES SEIN? The latter question (of which the first is a translation) appears in the manuscript of Beethoven’s String Quartet number 16 in F major.

Third step: “The penultimate element of the first version is one of four that share identical components, as described by a five-letter definition concealed in the grid.” Taking “element” to be a letter, the “penultimate element of the first version” is the letter B, which is — · · · in Morse code. Taking “component” to be a dot or a dash, there are three other letters that are encoded with the same set of components: · — · · is L; · · — · is F; and · · · — is V. The five-letter word concealed in the grid was PAEON, “a foot of four syllables, any one long, three short”.

Fourth step: “These four elements and another five-letter word must be highlighted to show key information relating to the question and an initial representation of the questioner.” It was notable now that the four letters B, F, L, and V appear once each in the grid. The “questioner” was L[udwig] V[an] B[eethoven], and the “key information” was F MAJOR.

Fifth step: “One of the four elements, interpreted differently, indicates which letter of which word in each non-misprint clue contributes to another message.” (This explains why some of the non-misprinted clues seemed rather awkward.) Well, the element that could most obviously be interpreted as a number was V. And the fifth letters of the fifth words of the non-misprinted clues spelled out DIAMETRIC EXCHANGES.

Sixth step: “The action it describes must be applied to the letters of the five-letter definition [that is, PAEON] (and their counterparts) to reveal a representation of that element which must be highlighted in full.” Swapping PAEON in the fourth row with IDTID in the tenth yielded DIT DIT DIT DAH, a representation of the Morse code · · · — for V.

The preamble promised that “all entries are words in both the initial and final grids,” and sure enough the diametric exchanges yielded new words: PYNE → DYNE, SQUARE → SQUIRE, PHAEIC → PHATIC, OLIO → OLID, TINNER → TINIER, PAINED → PANNED, DOSE → OOSE, OCTANS → OCEANS, THINKS → THANKS and DEED → DEEP.

Seventh (and last!) step: “Finally, the key information must be modified to provide a consistent rendition.” Now, DIT DIT DIT DAH is not only the Morse code for V, but a representation of the opening motif of Beethoven’s Symphony number 5 in C minor. And sure enough, changing F MAJOR to C MINOR yielded new words: FONE → CONE, TACKY → TICKY, and A MAJORI → A MINORI.

The last movement of Beethoven’s String Quartet number 16 is headed, “Der schwer gefaßte Entschluß” (the difficult resolution). It was quite the reverse in the resolution to this puzzle: the well-written preamble led me very smoothly through the complicated series of messages and transformations. If anything, I was slightly disappointed at how straightforward it all was. But any disappointment is overwhelmed by my awe at the amount of thematic material Shackleton managed to cram into this puzzle.

I’m not sure about the title. Perhaps it’s an answer to the thematic question?

As I started this puzzle, my recollection of Shackleton from the Listener dinner in Chepstow was of a relaxed, easy-going bloke interested in hill-walking. Little did I realise that, behind that innocent looking exterior, an evil genius was lurking! This is his third Listener, the previous two being 3887 Count Down to Re-entry about Bela Lugosi, and last year’s 3041 Much Ado About Nothing about Jackson Pollock, and absolute hell to check!

The preamble had lots of segments. The correct letters of misprints “reveal hints for deriving two versions of a question”; that sounded as though some sort of mental jump might be required, and I’m often not very good with those! And then there was key information (sounds musical) and an initial representation (a person’s initials) which must be highlighted. And that was only the first paragraph! There was only one thing for it … just solve the puzzle and take it from there. How often have I said that?

Well, that was the easy bit!! Actually, it was the fairly easy bit. I don’t know how long it took, but it wasn’t five minutes. I couldn’t blame the clues since they were very fair and, in some cases, an absolute joy, especially …

19ac: Perhaps referring to stroke in eighty year old, retired — ultimately monoplegia’s assumed  (eighty → eights)
38ac: Ely cathedral in need of repair — odd details withheld  (Ely → Sly)

Some of the misprints were a little more cunning, and was 1dn quality of mage or quality of magi? Time would hopefully tell.

So, on to the final step (which, for me, turned out to be more like a marathon). First of all, there were the extra letters: DOT ONE’S I’S AND CROSS ONE’S T’S for the acrosses, and EDDY/IDDY UMPTY for the downs, EDDY being the most likely. (Those of you not side-tracked at this point are lucky!) Looking the first saying up in Chambers gave to pay great attention to detail. Well, I try and do that with all Listeners these days, especially since I’m over a year without a mistake (as far as I know). And eddy and umpty looked like they could be a headless TEDDY (Andy Pandy?) and HUMPTY (Dumpty); perhaps the theme was going to be children’s games or nursery rhymes. The hidden five-letter word was PAEON in the fourth row, which is a foot of one long and three short syllables (in any order). So perhaps it does have something to do with nursery rhymes or poetry.

It was about this time that I noticed that the grid was pangrammatic, and that had to be relevant. Also, the title Sine Qua Non contained one each of the five vowels, and Shackleton has no repeating letter. I was on to something, wasn’t I? No I wasn’t. Nothing really helped here.

Back to the messages. I couldn’t see how the across one could be used to interpret the non-misprint down clues, and spent some time just staring at the grid. As has happened a few times recently I got that horrible feeling that I wasn’t going to solve this one. It is easy to get stuck in a rut and not be able to think outside the box (horrid expression!). I consulted my Top Tips for the Listener (especially if you’re stuck), and found the following:

Rule 4: In any message, do not dismiss a weird sequence of letters just because it is a weird sequence of letters.

I had looked up EDDY, but decided to try IDDY, and there it was, IDDY-UMPTY, military slang for Morse Code, which tied in nicely with PAEON. So this puzzle was about Morse Code, not nursery rhymes! It wasn’t too long before the letters B, F, L and V crystalised as each being one dah and three dits. Superb, and a warm tingly feeling ran down my spine as I shaded in the only occurences of these four letters in the grid. Rereading the preamble for the umpteenth time, I decided to look up the four letters in the Oxford Dictionary of Quotations. Voila! “Do you spell it with a ‘V’ or a ‘W’?” inquired the judge, referring to the spelling of Sam Weller’s name in Pickwick Papers. The warm tingly feeling evaporated as this led absolutely nowhere!

It was only when I decided to use my yellow highlighter that the initials LVB seemed so obvious, and things really started to fall into place. I had tried the first letter of the first word, second of the second, etc, but had made a silly transcription error when copying the clues to paper, so I failed to see DIAMETRIC EXCHANGES at letter V of word V. That may well have speeded things up earlier on, since it enabled the DIT DIT DIT DAH to reveal itself in row four after the swap. Exactly when or how Beethoven’s Fifth came into my head is difficult to say; I just found myself dah-dah-dah-dumming it! And it was in C Minor, enabling FONE to become CONE and A MAJORI to become A MINORI.

I finally realised how to translate the non-misprint down clues into one of only two quotations ascribed to Beethoven in ODQ: Muss es Sein and Must it be. Hence the two versions referred to in the preamble.

The puzzle had one last, albeit unintended, trap. Rule 2 in the Top Tips for the Listener (especially if you’re stuck) states “After filling in the across answers in your final submission, double-check against the downs. Even though I had caught a transcription error (I had entered MEIN for MIEN at 46ac), I got a horrible sick feeling in my stomach, realising how close I had come to making a mistake.

I don’t think that I can understate what a tour de force I feel this puzzle to be. So many wild goose chases (for me at any rate) and an absolute joy at every level. Whatever thoughts go on in your head, Shackleton, a thousand thanks for them, and here’s looking forward to your next puzzle. I hope I have a vote for the Ascot Gold Cup come year-end so that I can show my appreciation.

“Having solved the clues, solvers must choose between 65,536 possible solution grids.” For a computer programmer like me, that number is instantly recognisable: it’s 2 to the power of 16. So perhaps there are sixteen choices that have to be made, each choice being between two outcomes.

Eight of those choices will come from the clues in group A, where “definition and wordplay … lead to two real words which differ by a single letter.” Another four choices come from group C, where there are four pairs of crossing entries which clash. That must mean that the last four choices come from group B, where “clues appear with the wrong number, and with the wrong entry length; solvers must determine the correct locations for answers”. It’s not clear to me yet how that’s going to work. Group D is, thankfully, normal.

Solving is pretty slow to start with, and I’m not happy with my first answer. 21a “Difficulty besetting Roman deity least inclined to generosity” seems to be “difficulty” ⇒ NET around “Roman deity” ⇒ ARES giving NEAREST. Unfortunately, Ares was a Greek deity. Maybe he counts as a Roman deity too, by syncretism? Anyway, I can’t enter this yet because it’s from group B, so let me press on.

After about two hours, I’ve got a bit over a quarter of the grid. See the diagram above right: lowercase letters indicates choices, and the pink cells are the locations of the clashes from group C. From group B I have NEAREST, SAMURAI, which looks like it goes at 1a, and HASH, which could go at either 21a or 35d.

I wonder if the way group B works is that there are four pairs of answers which differ only in unchecked cells? That would mean that I need another entry fitting SAM_RA_. Aha! “Rodent hidden in regiment’s fruit” ⇒ SAMARAS, and “Poet’s injuries to beloved” ⇒ DEAREST. So I can fill in the checked letters from these, even though I don’t yet know which goes where. See right.

Now, I have a SAMURAI, and at 17a it looks as though there might be a WIFE if the clash there were resolved in favour of the W. The instructions for resolving the clashes is that they should “complete a full set of thematic elements derived from one of the titles”. So is one of these “thematic titles” that I’m looking for RASHOMON? I think it is, because the title, “The Fragmentation of Reality”, could work as a loose definition of the Rashomon effect, the storytelling technique from the film, whereby different witnesses to an event describe it in inconsistent ways. Also I can see 27d “Learned man named after god” ⇒ PANDIT which will become BANDIT after resolving the clash. Also, 16d “Wretched publicity for dye” ⇒ WOAD, and 30d “See unqualified tailor” ⇒ CUTTER: after resolution of clashes these will combine to read WOODCUTTER.

And now that I know that 17a is _IFE, I can solve “Part of earth according to hypothesis not admitting uncertainty” ⇒ NIFE. I note that had the clash been resolved as N, this would leave the word SERONS. So perhaps all the other clashes yield words however they are resolved?

With all this material inserted, the grid is about half full.

41a has a choice too: it could be TEHRS or TAHRS, but as it’s a group D clue I think this is a standard Listener trap for solvers rather than a thematic choice. “Pitches invaded by 200 goats, not 1” suggests the wordplay H in T[i]ERS, except that I’m not sure I can justify “pitch” = “tier” from the various senses given in Chambers. For “pitch” Chambers has the sense “degree esp of elevation or depression” and for “tier” the sense “row, level, rank, or layer”. Are these close enough? Anyway, I can’t find any justification at all for TAHRS, so TEHRS goes in.

I don’t understand the wordplay for “Pious fellow’s lost head over Scottish cook”. It seems like it ought to be STOVE (a Scottish word meaning “to cook”) but how does the wordplay work? ST OVE[r] is no good, since R is not the “head” of OVER.

Nonetheless, STOVE must be right, because I can see RASHOMON hidden at centre left. That means that the last answer from group B must be “Refuse to strip off initially in old-fashioned drag” ⇒ RASH and indeed the wordplay yields [t]RASH.

The last third or so of the crossword goes quickly, and soon I have all a complete grid, with sixteen choices to make.

So, how do I resolve all of these? Three choices from group B are needed to display RASHOMON, so the remaining choice (SAMURAI/SAMARAS) must reveal the second “thematic title”. I can’t see that yet.

The choices from group C display the four witnesses from Rashomon.

What about group A? The rubric says, “One letter from each differing pair must be entered so that the affected cells spell out a thematic name.”

So the thematic name must be [Akira] KUROSAWA (the centenary of whose birth will be on March 23). Unfortunately, this doesn’t completely resolve which letters to pick, because there are the pairs MINAR/MINOR and ARISTA/ARISTO. I’ll need an A from one and an O from the other. Aha, I see: if consider the cells in grid order (across the rows from top to bottom), then it has to be MINOR and ARISTA.

That leaves one choice (SAMURAI/SAMARAS) which must reveal the second thematic title, presumably the one in which “one character will take on a greater than normal significance and must be ringed”. Here a disadvantage of my working methods becomes apparent: I create the diagrams for this blog as I go along, entering answers on the computer instead of in the newspaper. And to save time and space I omit the entry numbers from these diagrams. Which means that I have been staring at the grid for a very long time indeed before it occurs to me that the second thematic title must be SEVEN SAMURAI, with the entry number 7 being the “character [with] a greater than normal significance”.