Harry is trying to trick you by leading you away from the best path forward. For 10A, look at the distribution
of EVERY OTHER letter. Then do the other half of the letters. Ignore digrams, unless you think you’re smart
enough to break a 676-symbol substitution cipher with a text of only 1203 symbols.
Not only that, but he picked out AN, which actually represents AN. The real question is what does
TT LW MM DJ EA OC DK UF LE represent?