1 no trump
3 no trump
2 no trump
The lead in all cases was the 7 of diamonds. One declarer played low from dummy and was forced to win the trick with the king. As a result, when West won the inevitable club finesse, nothing was left to his imagination. Proper technique calls for the queen at the opening trick, because it will leave West in doubt when he gains the lead with the king of clubs. West knows that declarer holds the king of diamonds; if it is still guarded, the play of the ace will establish another winner for South. So, in some cases, West decided to exit with the jack of hearts. Of course, South promptly ran for cover.
At one table, South made the right play but the wrong face. He won the first trick with dummy's queen of diamonds, but when the club finesse lost there was a distinct falling of declarer's chin, which West did not fail to observe. So, when West took his king of clubs he promptly played the ace of diamonds and struck oil. A cheerful front by declarer might have rendered West's problem more acute.
Emoting aside, West's play of the diamond ace at trick three is logical. He must realize that no effort to get partner in posthaste is apt to succeed. The bidding fairly marks declarer with both major aces so West's only real chance is to play for the king of diamonds to fall.