Despite Malone's pointer I am still not seeing what should be obvious. I have all the misprints - two of which I have in the same square -and correct letters but can see only one obvious sequence of six letters running diagonally downwards from the second letter of 17 across and starting and finishing with one of the misprints. I suspect that might be a red herring. Any pointers in the right direction would be much appreciated.
Alwayspuzzled, your thoughts about that diagonal, from the second letter of 17 A, are correct - but you need to take it a little further, literally! To see what's going on, look at the whole of centre row - that should give a big pointer.
Dear Malone
I can see the "Do not cross" message in Rows 5 & 6, and "Do not" twice in diagonals in the bottom right" These 2 "cross" each other. Also the 6 letter word from 2nd letter of 17A, and "line" diagonally from 2. But I cant see what to draw.
police do not cross.....wherever you see this or bits of it draw a thin blue line...from the L in 2 diagonally to the bottom R
from the S in 16 diagonally to the I
whole of row 6
and 1 more diagonal going the other way from the T in 9 d to the I on bottom row