1 and 20 across If this were so, one of them might be chow time. (5,3,3,3,3)

 9 Not a wrestling throw—it’s a more genteel game. (4,4)

10 If you have to, something may have been mislaid in the shuffle. (6)

11 Detains the alternative possibility? (7)

12 There’s a point to what might be associated with an artist. (7)

14 An opening in a small part of the school associated with marine life? (6)

15 A petty annoyance, if Beatle-arranged. (8)

17 Tend to be wary? (4,4)

20 See 1

22 See 13 down

24 Run by a poor navigator? (7)

26 The Mikado’s cloth might prove false. (6)

27 Someone might read 3 to try and calm one. (8)

28 Not what Mae West intended for her invitees, though the brash are more likely to get theirs. (11)
 

 2 and 25 down A bad poet gave blues a first presentation, as a matter of course. (9,4)

 3 Implying Brazilians are noted for their diplomacy, although it could be a disturbing incident. (4,3)

 4 and 8 In the publishing business, do they offer this for protection? (You might, before going out, if you’re worried about a suit.) (4,6)

 5 Closely related to Gothic character? (7)

 6 Put two and two together. (5)

 7 The flower of Cadiz, in Niagara now. (6)

 8 See 4 down

13 and 22 across One of the things the detective is, only? (One might not like to be such an accessory.) (5,3,4)

16 See? (9)

18 The city, as it should be about that time. (6)

19 Grow together with the current island combination. (7)

20 Tipsy with drink? That’s what some Britishers get in the afternoon! (4,3)

21 The plant’s yearly report, obviously. (6)

23 Some distance to travel in the north central region. (5)

25 See 2 down