The unclued lights, in one case paired, are all suggested by a thematic phrase (two words), which is set out in an appropriate form in the grid and must be highlighted.

Across

1 Brass and slate vessel (8)
6 Really humid round townships (6)
10 Ham cast chose plays — they cause discomfort (12)
12 Society cuts old displays (5)
13 Ape-like evangelical with outstanding pledges (7)
15 Beer and staple food one leaves in wood (6)
17 No gin in a sozzled artist (8)
20 Picture takers like river in Iceland (8)
22 Draw close, at first, in nocturnal habit (7)
24 See cuckoos and dogs (5)
26 Overcook, taking week to act like Ramsay? (5)
28 Qualification for business, having trouble in capital (7)
34 Rampant elitism’s most disgusting (8)
35 Ten jockeys needing a mount (4)
37 Snakes by golden castle (7)
38 The foreign fashion for singer (5)
39 Test hearing, with everyone in favour (12, two words)
40 Theft of inferior horse unacceptable (6, hyphened)
41 Part of dance considered in stages (8)

Down

1 Southern country, internally corrupt, gets sanctions (8)
2 Glowing wood on home fire finally (6)
3 Shell’s firm, almost more twisted (6)
4 One tucking into dessert before noon, salivating as expected? (9)
5 Formerly inflamed American finished penning chapters (8)
6 Fire consumes international vessel in Med (5)
7 Move nimbly having year off alcohol (5)
9 Haunt old ship carrying disease (6)
11 Youngsters to swim in Calais in northern river (9)
18 Painter about to bring back excessive style (9)
19 Those who strive on-line to get ladders (7)
21 Girl from Rhode Island blocking tax on salt (9)
23 System’s empty — nobody stood up for communications device (8)
25 Awareness one’s lost for life? (8)
27 Monkey from west lives with monkey (7)
29 He struggles to comprehend compilers in The Spectator (6)
31 Part of brain contains silicon particles (6)

A first prize of £30 for the first correct solution opened on 26 October. There are two runners-up prizes of £20. (UK solvers can choose to receive the latest edition of the Chambers Dictionary instead of cash — circle the word ‘Dictionary’.) Entries to: Crossword 2232, The Spectator, 22 Old Queen Street, London SW1H 9HP. Please allow six weeks for prize delivery.