This hand came up on Monday night and every West player in the correct contract of 4 spades went one down. Why was that?
North opened the bidding with 3 clubs, East doubled, South passed and West bid 3 spades, raised to 4 by East. North led out the ace followed by the king of clubs, West ruffing. Trumps were cleared in three rounds leaving one trump in both East and West hands. How should you tackle the hearts and diamonds?
The answer to this question lies in looking at the whole hand. With the club ruff there are 9 top tricks so only one more is required. If the hearts break 3 - 2 the 10th trick will come from your fourth heart and the contract is unbeatable; you will have just one loser in clubs, hearts and diamonds regardless of where the diamond queen lies. But, if the hearts split 4 - 1 or worse, you will have 2 heart losers and cannot afford to lose a diamond trick. For this reason it is a mistake to take the diamond finesse without knowing the heart distribution - you risk the entire contract when the finesse fails - and this is probably where all the Wests went wrong.
So, before touching diamonds you should play off the ace and king of hearts. If both opponents follow suit the contract is in the bag. As the cards lie, North discards on the first heart and you realise South will score 2 heart tricks. Is that a problem? Not if you let South have those 2 tricks because they will then be end-played, forced to lead a diamond away from the queen or give you a ruff-and-discard by leading a club or the last heart, giving you your tenth trick.
What if North shows up with four hearts? You still risk losing a trick to the queen of diamonds, but you know a lot about North's distribution. For his opening bid he should have 7 clubs, we've seen one spade and now 4 hearts, so he can have only one diamond. After the ace and king of hearts, cash the ace and king of diamonds (in case he pre-empted with just 6 clubs) to remove his exit cards and give him the two heart tricks. With no diamonds left North will have to give you a ruff-and-discard when he leads a club.
Why was this play so hard to find? I suspect we are over-trained to look at establishing tricks and under-trained at preparing the ground for throw-ins and end-plays. The spot cards in hearts are so low there is no hope of establishing anything extra whereas the diamonds offer a 50% chance, and this, combined with a lazy hope that the hearts would break 3-2, lured several Wests (including me) to take the early diamond finesse, to their cost.
Incidentally, the North/Souths who ventured on to 5 clubs deserved better results than they actually achieved.