I am relatively new to Spectator. I have solved all the normal clues but am a bit unsure of the unclued lights - are they all words with 2 consecutive alphabetical letters in them? This seems to work for 7 of my clues but like JRS I can't find a fit for 20d, having been right through Chambers for all possibles. Or am I on the wrong track altogether?
I think it's unkind to give the show away at his stage of the game; look at the title of the puzzle, which is very revealing, and mark well "the correct identification precludes any apparent alternatives"
Your interpretation is incorrect, by the way