Some random musings, easily dismissed....
Recent Listener threads have noted a perceived dumbing-down of the puzzle and complaints that it is "not like it used to be". Is there some chance that forums such as this one might contribute to that phenomenon? Sabre has produced a very tough puzzle here, and within a day or two all the information needed to crack it appeared here.
Note, I am not re-opening the debate about giving away answers - that's been settled definitively, and I certainly have done my share in that regard. So, giving away answers is fine, no complaints about that from me,
But, consider a setter's perspective - having created such a puzzle, which must have taken a long time, where should I submit it? I think I would favor a venue that is not openly discussed on the internets, e.g. the Magpie (whose C- and D-level puzzles routinely put the Listener to shame). Perhaps the "ace" setters of lore have simply taken their ball to another court, so to speak.
Or, we could be in for a run of 10 stinkers in a row, who knows? In any case, in a development which will disappoint no one at all, to be consistent I will not be contributing any more answers/hints to these threads. However, I wish you all happy solving (and, to be clear, happy hint- and answer-giving).