This for me has turned into another of those deeply frustrating ones where the penny refuses to drop. I have the whole grid fill completed including the isolated ones, and can only see one logical way to divide the double letter square, even though it appears trivial. I have the locations, but their collective hint doesn't go anywhere yet, and the "subject" (the obvious one?) and year remain stubbornly elusive.
Whether the opacity is influencing my judgement I can't tell, but I'm not that impressed by any of the clues (sorry!)
I expect when (if) the penny drops I'll be more impressed, but as it stands (and I can't see what difference locating the subject and year makes to the final grid, as there's no highlighting requirement) I'm rather underwhelmed, especially given Shackleton's previous efforts, which I loved - especially the Pollock. I'll get back to you all!