4115 Invisible Ink II by Sabre

This was a remarkable construction which showed how what seemed at first sight to be an impossible task could be completed by following a logical process. Half of the clues were presented in invisible ink, and the answers to the remaining clues were to be entered in encoded form, the letters A to Z each to be encoded by using a different letter.

The first step was to enter the known answers in normal text and then attempt to reverse encode the answers to the invisible ink clues. These had to be deduced one at a time starting with the answers for which all the letters were available in encoded form. The key to the puzzle was to tabulate the frequency distribution of the known letters in the grid, and making the assumption that these letters would approximately follow the distribution of letters in normal text. This showed that the top ten letters in the grid were OEATBILPR. These were assumed to represent a permutation of ETAOINSHRD.

Attention then turned to the completely filled BEBOPBOP, which used three of the top ten letters. After a long process of trial and error using permutations from ETAOINSHRD, the answer NONSENSE was found. Setting all relevant cells in the grid to these values led to SYNAESTHETES, and so it went on. At each stage a reducing number of options for the yet-to-be-discovered letters narrowed down the number of possibilities for remaining invisible ink answers. This involved a lot of dictionary searching but achieving the end result made all the hard work worthwhile.

In invisible ink answers, A to Z were represented  by CNMRO*ALT*GZDUSE*HBI*YP*Q*, * being an unused letter.

Grid entries for invisible ink clues are indicated with [].

Across
1 CECA
5 Bowled well, carrying half of Oval – a surprise down under? (8)
BOILOVER [NSTZSYOH] B (Bowled) + OILER (well) containing OV(AL)
11 Bird book leads to amateur recognizing flutter (6)
BARBET [NCHNOI] B (book) + A R (first letters of Amateur Recognising) + BET (flutter)
12 GAY-YOU
14 CUTE
15 Clock, wobbly to a large extent, confused everyone (8)
BLOWBALL NZSPNCZZ] BLOWB (anagram of WOBBL[Y]) + ALL (everyone)
16 Hound returning along with newspaper (6)
TALBOT [ICZNSI] TO (along with) + BLAT (newspaper), all reversed
17 CAMEO
18 Cut off a little terrine de foie gras, for example (9)
APOCOPATE [CESMSECIO] A + POCO (little) + PÂTÉ (terrine de foie gras, for example)
20 E-LA
22 Small number in narrow-minded Aussie crew (8)
BIGNOTE [NTAUSIOR] N (Abbreviation for “number”) inside BIGOTED (narrow-minded)
25 Dowse with rod dodging big trees (8)
REDWOODS [HORPSSRB] Anagram of DOWSE + ROD
26 OUS
27 Subdue unruly workers’ cooperative: no CEO at risk, surprisingly (9)
OVERPOWER [SYOHESPO] Anagram of WORKER’S CO-OPERATIVE less anagram of CEO AT RISK
30 ZYBAN
33 EXEQUY
34 SCALDINI
35 Currency replaced at million to one: some quintillions needed (4)
INTI [TUIT] Hidden in quINTIllions
The Inti was replaced by the new Sol in 1991, one million Intis being worth one new Sol.
36 Hollow girder over the top of cave (6)
GROTTO [AHSIIS] GR (First and last letters of GirdeR) + OTT (over the top) + O’ (of)
37 Urge cutting line, involving a verse poet’s set in stone (6)
IMPAVE [TDECYO] IMPEL (Urge) less L (line) containing A V (verse)
38 BOTANISE
39 SLAB
 

Down
1 Allow a cricketer what’s left of éclair (5)
ABATE [CNCIO] A + BAT (cricketer) + E (leftmost letter of Éclair)
2 Swagger about in pyjama’s top and bottom (7)
PANACHE [ECUCMLO] A (about) inside P (forst letter of Pyjama) + NACHE (bottom)
3 Covers for seeds, half of each bear snails (5)
ARILS [CHTZB]
4 ANENCEPHELIA
5 NONSENSE
6 SIZISTS
7 White radish: knife’s cut out work of art (4)
IKON DAIKON (White radish) less DA (knife)
8 SYNAESTHETES
9 OOZE
10 HUZOORS
13 The old annul caveat, being out of order (6)
VACATE [YCMCIO] Anagram of CAVEAT
19 SUBOXIDE
20 Texan introduces prostitute to fine son (7)
PROLOGS PRO (prostitute) + LOG (fine) + S (son)
21 AROBAS
23 ARPENTS
24 OUGUIYA
28 Sabre’s Chinese upset talking bird (5)
MYNAH [DQUCL] MY (Sabre’s) + HAN (Chinese), reversed
29 Climbers I see finally changing direction (5)
IVIES [TYTOB] I + VIEW (see) with W (West) changed for S (South)
31 Skein of geese are a very approximate ell? (4)
VARE [YCHO] V (Skein of geese) + ARE
32 Away from the city, lug some provisions to truck (4)
STOT [BISI] Hidden in provisionS TO Truck