12-AC by Apt

Four thematic names have become involved with 12-AC, and each appears as such in the grid, split across two entries. For three of these pairs of entries, the definition in each clue indicates the word in the other entry. Solvers must highlight the remaining pair. A thematic title appears at 36-AC.

1 Booth for one with two mugs in? (8)
7 Setter sheltered several ones (5)
12 See preamble (10)
13 A certain national regalia's unusual name (8)
14 Country’s flexible exercise of guile gets Government ousted (5)
15 One reading barcodes start to finish for Heinz etc (7)
17 Eye of thunderstorm is, surprisingly, to avoid its target (4)
19 Increasingly emotional row captures attention (7)
21 Enlarged cell block leads to assistant supervisor’s spat with copper (5)
24 Paper boys, after growing up, serve as leaders (5)
26 New hat, no trouser pockets and so forth (7, 2 words)
31 Bring back special festival (4)
33 Ian's continuously occupying island state near Brunei (7)
34 A nobleman beheaded a priest (5)
35 Catherine, cooking without recipe, becomes prickly (8)
36 See preamble (10, three words)
37 Trouble in Benin's intelligent society (5)
38 Observe New Zealander's restless energy at close quarters (8, three words)
1 Monkey poo used in US when raising plants (7)
2 Birds alone: empty nesters? (6)
3 What's kept in spare napkin ring? (5)
4 Someone online: less loud and more confident (5)
5 Make a jet pack sputter with last of power (5)
6 A large number in Japan like a fight (6)
8 Harry I name as a friend abroad (5, two words)
9 Let nine off, being this? (7)
10 Referee's assistant is conscious of missing header (4)
11 Letters from former lovers (4)
14 Comfortable with weapon (4)
16 English king's distressed call to protect sacred site (5)
18 Time component dropped from SI unit in scientific movements (7)
20 Dodgy characters sell knackered pheasants (7)
22 Type of gun with small barrel (4)
23 Product made from coal within small valley (6)
25 Son's spiteful and disorganized (6)
27 Bikini, perhaps held up by Sellotape (5)
28 US lake that Hoover visited regularly (5)
29 Rip off present’s wrapping paper at last (5)
30 Abandon party with a positive attitude (5)
31 A bit of spit and polish (4)
32 Make heavy demands on advanced classes? (4)
To enter this competition, send your entry as an image or in list format giving the highlighted entries to ccpuzzles@talktalk.net before 8th May 2019. The first correct entry drawn from the hat will receive a book from the Chambers range, which has been donated by Chambers.