The initial grid, filled with the clue answers, is shown here. The letters that were omitted from the two-letter cells formed POLYGONS, puzzles published in the Times Saturday Review. The corrections to clue misprints spelt out “nine-letter ones round mus; chi starts, zeta ends”, describing nine 3×3 Polygon puzzles centred on cells marked with Μ (mu), as shown in the second grid here.

(The Polygon answers using all of the letters in each case were: BRIEFCASE, LACONICAL (or CLOACALIN or CLOACINAL), OBFUSCATE, INUMBRATE, GOSLARITE, ACANTHOUS, CEDARWOOD, PERSUADER, ALBESCENT.) A word was extracted from each Polygon, starting in the Χ (chi) cell, including the central letter according to Polygon rules and ending in the Ζ (zeta) cell. The word lengths were given by the positions of each two-letter cell’s “surviving” letter in the extra word or phrase that defined the resulting entry. The extracted words were “erase all; obfuscate eta; sort out Codeword; use beta”. The contents of all cells were then cleared and the Η (eta) cells blacked out to form a Codeword puzzle (also from the Saturday Review), using the numbers given at the top of cells to encode the alphabet. The puzzle’s title could be read as “L is ten” to give a start in solving the Codeword.

In the completed Codeword, shown in the third grid here, the answers starting in Β (beta) cells gave the instruction “erase all but tau entries; solve letter sudokus; use kappa”. All cells were then cleared again, except for the letters in Τ (tau) cells, leaving the grid to be interpreted as two 9×9 Sudoku puzzles side by side (using nine letters in each, instead of the digits 1 to 9).

In the solutions to the two Sudokus, shown in the fourth grid here, the letters in Κ (kappa) cells spelt “erase; enter original nus”. Thus all cells were cleared again and the the initial grid’s letters from the Ν (nu) cells (shown in blue in the first grid above) were re-entered, spelling SI AENIGMA REQUIRIS, CIRCUMSPICE (if you require a puzzle, look around), a variation of Christopher Wren’s epitaph in St Paul’s Cathedral, “Lector, si monumentum requiris, circumspice”.