WEST NORTH EAST SOUTH (Dlr W, Vul NS)
1D - - 2S
3D 3S - 4S
West starts with two top diamonds against your contract of four spades. You run the second round and lead a club to dummy's jack. East wins and returns the eight of hearts, on which you play the nine, West the jack, and dummy the ace. How should you continue?
Since you have a loser in each of the side suits the problem is to avoid losing a trump trick. Other things being equal, the percentage play is to lead the jack of spades from dummy and run it if East plays low. But if you cast your mind back to the bidding you will realize that other things are far from equal in this case.
Although he was not strong enough to keep the bidding alive after his partner had opened with one diamond, East has already produced the ace of clubs. It is not reasonable to expect him to have the king of spades as well. With seven points he would hardly have passed his partner's opening bid.
Your only chance is to play the ace of trumps on the first round in the hope that West's hand is something like S K, H KJxx, D AKQJxx, C xx.
The ability to drop singleton kings has long been regarded as one of the hallmarks of the expert card player, but in this hand nothing more difficult than counting up to seven is involved.
This challenge hand is taken from page 53 of Hugh Kelsey Advanced Play at Bridge (Faber, 1968) - one of the many great books in our borrowing library.