3921 Mistaken Identity by Duck

As might be expected from a St. Patrick's Day crossword, Duck's Mistaken Identity took Ireland for its theme. What might have been less expected was this precisely constructed puzzle's use of latent letters (as opposed to the more common misprints or extra letters in wordplay) as the mechanism by which the theme was revealed. Definitely appreciated.

The unclued answers CENSURER, GENTLE, LUST, ROMANIST, and HUNT together comprised an anagram of CONNAUGHT, LEINSTER, MUNSTER, and ULSTER -- the four PROVINCES OF IRELAND, spelled out from the letters omitted from across answers.

Omitted letters are given in boldface type.

ACROSS
1 Membrane -- it protects that bone (7)
SCAPULA (CAUL in SA)
6 Each of them has a ball, glides around (7)
RIDGELS (GLIDES anag.)
12 Half-heartedly mumble support, backing location for planes? (9)
ARBORETUM (MUTtER BRA rev.)
13 Italian city friendly to English (6)
VENICE (E + NICE)
14 Study lawsuit, having to put out a brief (7)
CONCISE (CON + CASE minus A)
15 To get sex appeal all round, settle bust (9)
INSOLVENT (IT around SOLVE)
16 Hard plate's as seen in Indian tree (6)
SCUTAL (UT in SAL)
17 Two litres put in bog? His storage space is better! (8)
CELLARER (LL in CARR)
19 Small creature kept outside net round plant (9)
MISTLETOE (MITE around LET + O)
22 Rotten Civil Service restricting politician in act (lO)
DECOMPOSED (CS around MP in DEED)
26 Stopped evil having got into tangle (7)
FORBADE (BAD in ORE)
28 Tribe's succeeded -- a people not dead (6)
SALIAN (S + A + LAND minus D)
31 Noticed dreadfully old-fashioned teaching (8)
DOCTRINE (NOTICED anag.)
32 Commonly used label love rejected (7)
VULGATE (LUV TAG rev.)
33 I keep being naughty sprite (6)
KELPIE (I KEEP anag.)
34 Firm contrived once to get around rule (9)
ENGRAINED (ENGINED around R)
35 Benches about to be invaded by fifty kestrels (8)
STANNELS (SEATS rev. around L)
36 Criticised a soprano for joining in mechanical performance (7)
ROASTED (A + S in ROTE)

DOWN
1 Product of smelting gives aromatic odour, they say (6)
SPEISS (SPICE homophone)
2 See preamble (8)
CENSURER
3 Muscle with electric current on -- twitching or lifeless (7)
ABIOTIC (AB + I + O + TIC)
4 Wearing nothing, one local boy catches cold (6)
UNCLAD (UN + LAD around C)
5 Goddess in cloak enthralling Irish broadcasters (7)
ARTEMIS (AMIS around RTE)
7 Drivel old lout comes up with (5)
DROOL (LOORD rev.)
8 See preamble (6)
GENTLE
9 Stratagem to avoid leader getting cut (4)
ETCH (FETCH minus F)
10 See preamble (4)
LUST
11 Mark is a catch, maiden admitted (5}
SMEAR (SEAR around M)
18 See preamble (8)
ROMANIST
20 With input of oxygen Bill becomes fitter (7)
TENONER (O in TENNER)
21 I slept awkwardly, nursing a bad foot (7)
TALIPES (I SLEPT anag. around A)
23 A curse upon old, old spirit! Feel loathing inside (6)
MAUGRE (MARE around UG)
24 The old man shown on front of ancient ornament (6)
PATERA (PATER + A)
25 Possible cause of blessing somehow seen in book of Bible? Quite the opposite (6)
SNEEZE (EZ in SEEN anag., ref. the Book of Ezra)
26 Old birds seen as rare idiots (5)
OAVES (O + AVES)
27 Put up grey piece of lead (5)
DRAIL (LIARD rev.)
29 See preamble (4)
HUNT
30 A contributor to coastal gastronomy (4)
ALGA (...AL GA... hidden)