Well that was a bit of a struggle but it all worked out in the end.
A beautiful construction and how agreeable to have a puzzle that when you have entered all the answers you have finished.
Slightly gentler than I anticipated, and I found myself searching the diagonals in the completed grid for nudges towards the inevitable Playfair coding that was required for the final step. Tough clues with obscure definitions: my nemesis was 4ac where I dismissed the only possible entry that matched the crossing letters because it was so clearly irrelevant - except it wasn't
Don't understand the wordplay of several of my answers, so not for me a very satisfying puzzle, although I enjoyed the challenge of cold solving some tough (for me) clues.
Late to the party here - catching up on Listeners after a holiday away from t'internet.
A cracking Sabre special - it all fits together so neatly when you get it right, but falls apart if you make even the tiniest slip (which I did - twice).