In this deal from the Sao Paulo State Championships, Joao Paulo Campos, West, doubled four hearts with his two aces rather than bidding on to four spades. The bad trumps and doubleton in hearts were bad signs. If East had a singleton heart, she might already have bid four spades.
Campos reasoned that there would often be only four trumps in dummy, in which case there would probably be compensating shape elsewhere, perhaps short spades. He led a trump to the eight, queen and ace. Declarer then advanced the club three, West taking the ace as East followed with the nine. What now?
Campos switched to the spade nine in the hope that his partner could win and play a diamond through, but that conceded the contract.
With no more tricks to come from clubs, perhaps East’s card ought to indicate suit preference rather than count. If East-West had that agreement, West might have reasoned, based on East’s club nine, that his partner held the diamond king. In that case, West should shift to the diamond queen at trick three, securing what tricks he can there, before declarer cashes the club king. Playing the diamond ace instead would make partner’s life unnecessarily hard — she would need to unblock the king.
Declarer could have made his contract without giving the defenders a chance. He should enter dummy in trumps at trick two and then finesse the spade queen. A diamond loser can then be thrown on the spade ace before a club is led.