After a straightforward auction, in which you admitted to three key cards and the ♥K, you land in 6♠. West leads the ♣Q. You win in dummy perforce. Now what?
After dummy won the opening lead, Declarer observed that he might have bid 7♠, as North was unlikely to have three low hearts. Even so, the contract would then have been no worse than on a 2-2 heart split, provided trumps were not 5-0. Declarer then reflected that such considerations were no reason to go down in a small slam.
After winning the first trick with the ♣K, declarer cashed the ace of trumps. When both opponents followed to the first round of trumps, declarer saw that it would be a mistake to draw a second round of trumps if both majors turned out to be 4-1, as happened to be the case.
Declarer reckoned that if he drew a second round of trumps when both majors were 4-1, he would no longer have the entries to establish the hearts. So declarer cashed the ♥A hearts at trick three and played a low heart next. Declarer was pleased when East showed out: in fact, he would have failed if he had tried to cash the ♥K! (East would have ruffed and returned a trump, preventing declarer from ruffing two hearts and drawing East’s last trump. Declarer would have had the dismal task of conceding a heart trick to West for down one.)
As it was, the defense was now powerless. West took the heart exit with the jack and played a diamond. Declarer won the trick with the ♦A, crossed to hand with a trump and ruffed a low heart with dummy’s queen of trumps. There was a trump left in the dummy, so declarer could draw East’s remaining trumps and claim 12 tricks. Declarer made four trumps, four hearts, a heart ruff and the three tops in the majors. The full deal: