No bar is necessary at the place you mention. We are told in the preamble that there are ‘unclued lights’ (plural), and there are two of them, one of which starts where the J is, the other being where the asterisk is. ]]>

Thanks for the blog. I’d like to take up this bit of space to relate my own experience of this puzzle.

It is the first numerical crossword I have tried for about 40 years, not counting an interesting puzzle last year, called Well Spoken, that was a combination of a cruciverbal and a mathematical puzzle, in which numbers played only a small part.

Having got going via the bottom middle of the grid I reached nearly halfway when I mistakenly eliminated 752 (the correct answer) at H. I had to scrap my partial solution and start again. When I realised that the asterisked number (the cipher key) had to be less than 28, but not much less, I entered 752 at H and got going again.

Solving this was great fun, and I admire the ingenuity that went into the design. Clue u (68) stood out as the most useless clue I’ve seen for a long time! It was of no use at all for solving either that clue or any other, and it is itself solved only by way of clue F, which in turn is solved with the help of both S and l.

When the grid was complete, it was clear that 25 was the maximum possible divisor for the key (otherwise the sum of all the digits would be too great), and it turned out to be exactly 25, my first try. When the message was deciphered it took a few moments for me to decide that some of the letters were not significant. What was left exactly matched what the preamble said was included in it.

My rustiness showed at first, but having worked through this at the second attempt I thought this puzzle was pitched well and fairly.

It was interesting (and deliberate, of course) that only four letters in the message (a P, D, N and H) were decipherable before knowing the divisor. It was just as interesting (and deliberate) that the first five letters of the message using a divisor of 25 were PCNOD. I think it was as much by luck as anything else that I went further, and after picking up the unhelpful combination DDDD I got the real message.

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