Outstanding clues, a very finely constructed grid and an endgame that was, thankfully, not too hard to work out. I have a feeling that it's the first, or maybe the second Shackleton that I've managed to complete.
I have some sympathy with tristram37 and Cloverjo. There have been quite a few carte blanche or semi carte blanche puzzles this year. I must admit that I found filling the grid of this one rather a slog. I don't think I was able to make a start on the grid until I had 24 or more clues cold-solved and even then I made several wrong guesses initially, because of the high number of 5-letter, 6-letter and 7-letter entries, besides other features of the grid. I only really started to enjoy it when I saw an alternative location for one entry that was causing me problems, after which I made far better headway.
Having said all that, the carte blanche approach is fully justified, even if it makes things tough. And, to be fair to the setter, many clues were not that hard to cold-solve.