ACROSS
1 Damage tree in 28? (5,3,6)
9/13/12 Squire Ambler caught Ned mixed up in 28 (10,6,5)
10 See 12
12/10/20 Reconstructed Siegel theorem in 28 (5-4,4)
13 See 9
16 Singer caught up in Hopi affair (4)
17 Dante, confused by witches, entered into agreement (10)
19/26 If not playing by ear, use fatted shed roof alternative (4,3,3,4)
20 See 12
22 Early prayers - or dawn chorus? (6)
23 See 27
26 See 19
27/23 ’Zat Brent’s drawls? May take place in 28 (2.,7’1,5)
28 Cleric, Laird, Chadian, Nick, Ian Og partake oddly in social activity (7,7)
DOWN
2 Emit wrong duration (4)
3 Exploring Tiber, Ian discovers peninsula (6)
4 Partial descent of audible ladder (2,3,3,2)
5 Lots of 2 (4)
6 Regard those another way (4,2,4)
7 Part-time saxophone player? (7,7)
8 Emergency worker north of the Border (5,9)
11 The quality is obviously the same (5)
14 Renaissance dance: ensemble (instruction) (5:5)
15 Wildly, Alec Walshe became Polish president (4,6)
18 Slice, or 13, or piper MacDougall (5)
21 Keyless or tribal - either will fit! (5)
24 Tich is irritated … (4)
25 … by Rona singing in Gaelic (4)

BLETHERSKITE