3 See 37 Down
9 The sound of 21, perhaps, may stop His Majesty from entering East End borough
(7)
12 Amicable split leaves French friend with no tie. (3)
13 Opulence without clue not closed (4)
15 A beach in Central London? (6)
16 Wanting existence? (9)
17 It's slippery going with the wind backwards. (3)
18 Slightly twisted shard of precious metal, maybe?
(6)
20 See 43
21 Messy assailant loses Asia then slopes away (5)
22 Branch of United Nations that deals with removal of weapons? (5)
26 Even a good seat needs a good seat. (6)
27 Magic spell or just a code? (3)
29 Take Little Dot up the Shard? Best day ever! (4,4)
30 Lean towards a Roman script? (6)
32 Mix up closes markets. (5)
34 Set out and stop abruptly. (5)
35 Somewhere to store artist? (6)
36 Tangled up in ropes with little chance of release. (8)
39 Initially, left wing historian. (3)
41 Queen Elizabeth follows art. Why? Because it comes from the heart! (6)
42 A fountain pen for 30, perhaps? (5)
43/20 Dark cur! Back gold for a good return.
(5,3)
46 Euphemistic reform? The Unions are upset. (3)
48 Divorcees I've taken out and had to adjust beliefs. (6)
49 Norway? No way it's conditional. (3)
50 One could be excused for thinking it might be used on a fingernail. (9)
52 Puck in bubble pack run off at the mouth (6)
54 Grating element in American Football (8)
55 Ear, Nose and Throat department initially takes on disturbed teen and develops an understanding. (7)
56 Sounds like someone tripped up whilst speaking. (3)