Jon has presented me with a Blueish Club bidding system, which I'm gradually getting to grips with. At matchpoints, and single dummy, you might be happy to reach 6NT on this deal and guess which finesse to take, but on the actual lie 6 by West is the only making slam. 4 in our auction showed a good 4-card suit and 14+ high-card points: when Jon invited me to pick a slam I thought that with my minimum values a diamond ruff might well be needed.
We were lucky that the conventional 1 opening right-sided the contract, that I stumbled upon sensible calls despite being a lot less certain of the meaning of the auction than I've made out, and that 6NT couldn't be made. But still, it's satisfying to make a Moysian slam.
However, one West had bid and made 6NT, presumably on the ace of spades lead. That would be the best lead if East rather than South held the queen of diamonds.