In today’s deal, South had no reason to contemplate declaring no-trump, so he rocketed into the spade game, and that left West to guess what to select for his opening lead. A club from the queen was too risky, but a heart seemed too passive. He struck the right balance with a diamond.
East took that with the diamond king and then cashed the ace. He knew from West’s lead of the fourth-highest diamond four that South had at least three diamonds and there was a ruff in the offing. East then had to find his partner’s entry. Looking at dummy’s heart holding, a club was the natural choice. Alas, declarer won and shrewdly took three rounds of hearts for a diamond discard before drawing trumps. Thus, he could overruff East in diamonds to come home in his game.
East was to blame here. He should have played his top diamonds in reverse order, to flag on the second round that he had a doubleton. Logically, this also demands a suit-preference card from West on the second round so that East can determine what is the best switch. On this layout, West can see that the natural club shift will not work; he should drop a high diamond, preferably the jack, to signal for hearts.
This is an impossible signal, considering the dummy, so it merely warns East away from a club shift. All that remains is the trump suit. A trump switch at trick three (however unlikely this may be in theory) secures the diamond ruff before declarer can get rid of a diamond on a heart.