How do you play four hearts after West leads the 10 to the queen and ace, and East returns the 4?
See what happens if you pitch a club and try to ruff both spades. You play ace, king and ruff with the J. The 3 is ruffed with the trump ace and the last spade is ruffed with the Q. Now you try the K but East wins to play another diamond. You ruff with the 10, while West discards. You try the 7, but West jumps on this to play the last spade, ruffed by his parttner's 5.
Now, the mighty 6 is the setting trick.
This actually happended to several declarers. I did see the acute problems of avoiding the promotion and paid careful attention to the return of the 4 at trick two. If East tought his partner was ruffing, maybe he was asking fror a club return. So I pitched a spade, played three rounds of spades, ruffing in dummy, then the A and 10. I ruffed the spade return, drew the last trump and played a club to dummy's jack.
Bridge Today, Nov-Dec 1993, p. 33 Barnet Shenkin