If, like me, you are in possession of an ODQ, you dislike detours, and you want to get this finished, my advice is as follows. To get the thematic PDM, don't bother with the "assistance" from the source indicated in the across clues' communal letters, or the one revealed by the down clues' communal letters, just look in the ODQ pages for 34 across. To be honest, I really enjoyed the clue solving and the grid fill, but had a bit of a "Meh" moment when I tracked down the theme. In fact, I really don't follow what the thematic reference is on about, but the word swapping and highlihting ARE obvious at the end, albeit, for me, a bit of a let-down. A great and enjoyable puzzle with a bit of a damp squib for an endgame. 8/10