Crossword Help Forum
Forum Rules

I have solved every clue, and have the appropriately punctuated message.
I have found five (all 8-letter, because I was only looking for those) 'variations of 7' whose creators' first names appear in the grid.
B__, V__, P__ all fit at 1ac; another B__ (whose first name is the diagonal one), and an A__ (whose first name is the horizontal one) do not fit and seem likely to be irrelevant.
Now I must apply the second sentence of the preamble. I suppose I must treat the unnumbered entry as being the result of
using an unspecified number of those techniques on a word, and reverse the process. (Though I find 'used' rather than 'you must use' confusing).
I cannot tell from the instruction how many operations I should carry out, or in which order - possibly two, but possibly more with the whole process carried out twice.
I understand that a common K__ fits at 1ac. Contrary to above comments, I cannot interpret the instructions in a way that further narrows down the possibilities for the K__ beyond what fits at 1ac. That is a very long list of words.
There seems to be too much uncertainty to start trying options.
Am I misinterpreting the instructions?

(I have scanned the list of words (also a very long list) that fit at the unnumbered entry and know by association what goes there, its number, the next member of the set, and where that goes. That does not encourage me to start experimenting to fill in intermediate steps)

Thanks, Turast. I could see an anagram but didn't think about it being a real name.

The obscure references to Scots or ancient terms always slow me down. And having to back solve every clue rather takes the fun out of it.

sounds like you’ve completed the puzzle but if you want to go through the intermediate steps the key piece of the the preamble that you haven’t interpreted in the right way is that the long instruction you’ve uncovered tells you that three things can go at 1a all of which have their founders name in the grid

JamesM, you and I appear to be at similar stages. I too found three variations of 7, beginning B, P and V, that would fit at 1 across. The only one of these which could be a K****** is the one beginning with B, because the others have letter(s) which repeat. I tried treating the un-numbered entry with these, but all that happens is that I end up back where I started and 28 down is a non-word at each stage. Initially I thought that this must mean that I had gone wrong somewhere, but having re-read the preamble I now think that there may be no need for this entry, or those crossing it to be real words. I have the first, second and third messages, no idea what the last one means and no idea where to go from here. If there is anybody still out there . . . HELP please!

0pt0
Your method is OK, perhaps you are executing wrongly?
Use P & V with B as K, remembering that you are going backwards through the process, and that either order is possible.
For P, look at its Wikipedia entry which has a helpful section on its application in Listener crosswords.
I'd say the preamble is unambiguous that all entries at every stage other than the original un-numbered one must be real words.

btw, there is no requirement for K's to have no repeated letters.

(This is an aside and would be a distraction here.)

In the method people have mentioned, a K...... can have repeated letters. The repeats are simply omitted in setting up the arrangement.

.... as James said while I was slowly typing.

Candledave, thanks. As you point out, I had omitted to apply the name requirement to the third thing that must fit at 1ac.
I have now worked out the missing steps. I felt like I'd better do that because the last two elements (those in the set) didn't seem like they were the meat of the puzzle, only confirmation that you'd understood the rest, which I hadn't.
Having done it, I am still struggling to understand the logic of the preamble's second sentence.
I can see that it is true, insofar as it refers to P and V. However, while it is obviously meant to lead one to B, it is not true as regards B. B is not a technique used in order to 29 the unnumbered entry, and yet it is referred to as such later in the preamble - "... linking the end result to the name of one of the techniques".

Just to add to your confusion - none of the 3 variations exclude K's with repeated letters. In the case you are probably thinking of, duplicate letters are allowed and all but the first ignored...

Yes the best of the year to date. The surface reading of the clues was excellent given the constraints of clue construction. The final reveal was stunningly clever.
One small query. What is the point of Mainland in 39. Chambers indicates the answer is an island feature.