I have finished the puzzle, including finding the author, the 6 names, and the alternative names for the 6th character but I'm still puzzled about the clash I have where 12D crosses 20A. I realise that the two letters that could fill this cell actually represent character 6 but this doesn't seem to be mentioned in the preamble. Have I made a mistake with one, or both of these answers? I can move on once I know!