I'm glad to have finished this one quite quickly. I've tremendous admiration fot those of you who carry on for a week or more wrestling with puzzles but I cannot feel enthusiasm for starting a puzzle if I can't reasonably see myself finishing it by the end of the weekend. So this is the first one I've tried since 4684 and it's in an envelop ready to go off. Its nature is that there are several details which I don't need to solve. Who cares that I haven't satisfactorily parsed 36A? Or whether the 3rd letter of the penultimate word in the message comes from 9d or 12d? I prefer a puzzle whose solution - though perhaps hard-reached - Is incontrivertibly the only one available. Which, I suppose, when I came to the endgame, this one is, even though one hasn't definitivly completed each stage in getting there.