Probably a Magpie B on a five point scale (other solvers will of course have different views). No small achievement at all to finish from a background of US style crosswords.
Harder puzzles do come along - we’re probably due one. See an explanation for a hardish one below.
Cheers.
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Two Solutions by Quinapalus
Puzzle explanation
The corrections to clue misprints spelt out “indices, surds; move both Xs vertically”. The grid entries containing two words gave Rev. C. L. Dodgson, his nom de plume Lewis Carroll, and the (abbreviated) titles of two of his books, Rhyme? And Reason? and Phantasmagoria (and Other Poems). A verse cited in both books includes:
Yet what are all such gaieties to me
Whose thoughts are full of indices and surds?
x^2 + 7x + 53
= 11/3.
The quadratic equation has two complex solutions, (−7 ± √(−445/3))/2, which are approximately x = −3.5 ± 6.0896i. Nudging the two Xs in the grid to a distance of more or less 6.1 cells above and below the central axis, encroaching on the previously empty cells to form new words reading across, marks the two complex numbers as in an Argand diagram.
For the cells containing two letters, it didn’t matter which (opposite) corners they were placed into, as long as the letters of each of the two entries, as well as ARGAND DIAGRAM, could be read normally, as stated in the preamble.