The unclued lights (one of two words — ignore its accent) are of a kind.
 

Across

1    I’m the proctor, circulating and turning away from the heat (12)
10    Stone, almost black, with one diamond inside (4)
12    Moonlight escape around river turning into a brief liaison (10)
14    Leader of Indians accepting thanks for miriti palm (3)
17    Architectural style representative of its time chapter omitted (5)
18    Macbeth’s query about his status, it would seem, is a gas (7)
19    Classify love-boat reflected in painting (6)
24    Office work nowadays managed at first at home (5)
26    Party with star prize (9) …
29    … New star, a Jamaican? (5)
31    Alice Cooper, initially, upset about US corporation (6)
34    It’s most advisable having a long time in the Street (6)
38    Little Sparrow consuming large rice dish (5)
39    Bone, green then black in time (8)
40    Openings of saunas provided at resort (3)
41    Film director is seen about ten drinking a little Irn-bru (10)
42    Favourite seated outside (4)
 

Down

2    Transfer missing date to one article from 1714 onwards (10)
3    Retrogressive delay introducing new vitamin A supplement (7)
4    Gear used initially on landing at dawn (5)
5    Where working hours are recorded by newspaper changing the Earth (9, two words)
6    Residents of holt or sett disturbed (6)
7    Up to scratch? (5)
8    Old capital fellow with two names (4)
11    Director General accepts popular crazy game (8)
16    Grass obtained from cobalt’s not odd (3)
19    Vessels round 29, floating (6)
21    Hearts paid out for lists of successful releases (10, two words)
23    Bird below heavenly body that’s often in leaf (9, two words)
25    Bones from long skirt with middle of hem all turned up (8)
28    Figure out pills during middle of the week (7)
30    Least honest HQ gets stumped (6)
32    Lincoln or some Studebaker turning up (3)
33    Prison officer’s wages (5)
35    Knight admitting gratitude for Scottish turnpike (5)
37    Upset not recorded. That’s bad (4)
 
A first prize of £30 for the first correct solution opened on 27 November. There are two runners-up prizes of £20. (UK solvers can choose to receive the latest edition of the Chambers dictionary instead of cash — ring the word ‘dictionary’.) Entries to: Crossword 2335, The Spectator, 22 Old Queen Street, London SW1H 9HP. Please allow six weeks for prize delivery.