Many years ago I remember Tor Helness, the great Norwegian champion, going into the semi-final of a world championship saying: ‘Whatever happens I am not going to make a mistake.’ They won (the final too, actually) and I asked him if he had succeeded in playing perfectly. ‘No,’ he admitted. ‘Nobody plays perfectly and I made two mistakes.’
If he can’t do it where does that leave the rest of us? It’s always worth giving declarer a guess if you can, even if s/he is a world champ (see diagram).
North-South has (in theory) done brilliantly in the auction, reaching a very playable slam with only 25 HCP. Hands with two sources of tricks — plus a couple of controls in the other two suits — can be extremely difficult to bid to the optimum contract; indeed, if West had raised the ante with a timely 4♣ bid, it would probably have been beyond them.
West led the ♥5, to the 8, 9 and Jack. Declarer teased with the Jack of Spades but got no reaction. He rose with the Ace of Spades, drew trumps and ran the ♠10 to East, who cashed a Club for one down. Bad luck! Well bid and well played — or was it?
Imagine South puts the Queen of Hearts up at trick one. He wins the King with the Ace and goes through the same process as before. When East wins the Jack of Spades, he has to guess if there’s a Heart or a Club to cash. He may get it right, but he may get it wrong. You have put him to the test.