This was a tricky one — not that there’s anything wrong with that! Tough clues plus the pairing plus the five made for heavy going while I was away on holiday…
I’m afraid I do agree with people from drxx@4 onwards who have pointed out some clue deficiencies, and I’m unpersuaded by those who have tried to be apologists. Tough clues I don’t mind, but there are some problems. Several people have mentioned 40a, and the problem there is there are several alternative answers that could almost work: for example, ASSES are also hoofed and BASSES are not exactly huge but are quite big fish. Sure, the actual answer is a better, cleverer fit, but near-misses like this are generally considered sloppy. There are also several instances of what I think of as a definition-chaining fault. One example: EE may be a Scottish word for ‘eye’, and ‘eye’ can sometimes mean ‘sight’, but that doesn’t make EE a Scottish word for sight.
Nevertheless I did enjoy this and some of the clues are very fine. I like the device of 6a and 14a (though I’m a little unsure about 14a — the phrase it relies on is not actually in BRB, which is a shame). The preamble, once understood, is very neat! It seems to me that the two names in the endgame could have been even more appropriately placed, but the endgame does work out nicely so all in all a decent puzzle.