Your partner’s 5NT bid was asking about kings and guaranteed all key cards and the trump queen. When you admitted to holding the ♥K, North felt he’d done enough because with solid hearts you would surely have bid 7♥ over 5NT. His bid of 6♠ left it up to you to bid the grand. You chose a conservative approach by passing 6♠. Against your small slam, West starts with the ♣Q. Do you see a way to 12 tricks on this deal?
Trick one was taken in dummy perforce. Declarer saw that if trumps were 5-0 he would be able to make the contract only if hearts were 3-2. So, declarer played a low trump from dummy to his ace at trick two. Relieved that the trumps were at worst 4-1, declarer cashed the ♥A at trick three. He was about to play the ♥K when a thought flashed into his head: “What happens if the hearts are 4-1?” Declarer pushed the ♥K back into his hand and continued instead with a low heart. West took this with the jack and, in response to East’s signal, exited with a diamond. Declarer won with the ace and asked himself whether anything could be done if East had started with four trumps headed by the 10. Demonstrating that there was an answer to this problem, declarer called for dummy’s ♠9 and won the trick with his jack. He ruffed a heart with dummy’s ♠Q, led the ♠5 and simply covered East’s card, drew the last trump and claimed the balance – making four trumps in hand, four hearts, a heart ruff and three tricks in the minors. The full deal: