SOLUTION BELOW
ACROSS
1 Mirror reflection (5)
4 Not funny! (2,6,6)
11 Personal teacher (5)
14 Coil of yarn (5)
15 Interruption or intrusion (11)
16 Moss type (8)
19 Abundant (7)
20 Group of eight (5)
21 Not observed (9)
24 Rule of personal conduct (9)
26 Favour (6)
27 Dive (6)
31 Major artery (5)
32 Decapitated (8)
34 Going down (10)
38 Golf course avenue (7)
39 Summer flower (6)
40 Reach (6)
41 Hobble (4)
42 Warrior (7)
45 Fantasist (10)
50 Occupied (7)
54 Ear part (4)
55 Insubstantially made (6)
56 Purpose (6)
57 Prevent possession of (7)
60 Conveying to addressee (10)
61 Dutiful (8)
62 Borders (5)
65 Rhyming writing (6)
66 Bends down (6)
67 Warned (9)
72 Noisy, tactless blowhard (9)
73 Fireplace (5)
74 Scouting activity (7)
79 Ancient language of India (8)
80 Fellowship (11)
81 Water vapour (5)
82 Given medicine (5)
83 Reminisce (5,2,3,4)
84 Beginning (5)
DOWN
2 Manufacturers (6)
3 Heartache (5)
5 Skip (4)
6 Coal pit (anag)(7)
7 Country with Jerusalem (6)
8 Horned animal (4)
9 Went up (8)
10 Fix (6)
11 Moving around (10)
12 Hue (4)
13 Contrition (7)
17 Utilising (5)
18 Amorous correspondence (4,6)
22 Relished (5)
23 Tempting (8)
25 Went to bed (7)
26 Hallway (7)
28 Red fruit (6)
29 Cured (6)
30 Author (6)
33 Stage play (5)
35 Stared open-mouthed (5)
36 Auction (4)
37 Placid (4)
42 Dense (5)
43 Tagged (8)
44 Monarchs (6)
45 Control, subjection (10)
46 Stringed toy (2-2)
47 Devastating (7)
48 Song of loyalty (6)
49 World-weariness (5)
51 Poverty (4)
52 Shorten (7)
53 Coveted (6)
58 Failed to notice (10)
59 Merge (5)
63 Imprint on envelope (8)
64 Neighbourhood pub (5)
65 Extolled (7)
68 Belgian port (7)
69 Habitual user (6)
70 Sermonise (6)
71 Breathe in (6)
75 Moutaineer’s spike (5)
76 Finishes (4)
77 Baby elephant (4)
78 Headlice eggs (4)