North’s bids of 2♠ and 4♣ suggested a modest hand with least four clubs and at most two hearts. South was happy to be in slam as long as North the ♣K, which was shown by the 5♦ response to the 4NT enquiry.
West led a low diamond. Declarer took East’s ♦K with the ace and continued by cashing the ace and king of trumps, discovering that East had started with three. As he had to develop a long trick in hearts, declarer cashed the ace and king of hearts, then ruffed a heart in dummy with the jack of trumps. East’s discard of a diamond meant that it was useless to ruff a second heart in dummy. Instead, when declarer returned to hand with the ♠A and played another heart, he threw dummy’s ♦10 on it, allowing West to win the trick, as East parted with a second diamond.
Declarer ruffed the spade continuation low in hand then ruffed a diamond in dummy. All that remained now was to ruff a spade in hand, draw East’s remaining trump with the queen and cash the established heart for his 12th trick. The full deal: