*I don't know why partner didn't respond 1D
** Your style is to cue first round controls only in this sequence (with 4NT to show interest with no control), so choosing to cue the SK implies very good trumps
I'm not asking for comments on the auction, but if I don't give it there will be complaints. You've ended in the right spot, which is the main thing.
Opponents in theory play standard leads and carding, but you have seen they generally don't bother signalling, and they may not religiously lead their systemic card against a slam.
8 of diamonds lead.
You win in dummy, RHO playing a nondescript low diamond.
Club to hand, all following.
Heart to the king and ace.
Club return, on which LHO discards a heart.
The speedball players now ruff a spade in dummy.
Do the players with more time available see a better line?

Help

1♣ 1♥*
1♠ 2♦ (FG)
3♣ 4♣
4♠** 6♣
P