"I calculated the percentages very carefully!" complained South after going down in his slam on this week's deal. His arithmetic was perfect but he had missed a not too difficult way of improving his chances.

Game all; dealer South North 4A Q 10 7

!A 5

pounds K Q 6 5 4

27 4

West East 42 46 4

!K Q 10 !9 7 6 4 2

pounds J 9 8 7 2 pounds 10 3

2Q 10 5 3 2A J 8 6

South 4K J 9 8 5 3

!J 8 3

pounds A 2K 9 2

South opened One Spade and North, taking a reasonably rosy view, forced with Three Diamonds. South rebid spades and North, in modern style, bid Four Hearts. He would not have forced on a two-suit hand, so this showed a control and agreed spades. With th e clubs protected and a key card in the diamond ace, South soon ended in Six Spades against which West led the king of hearts to dummy's ace.

There were two main chances: the ace of clubs could be right (50 per cent), in which case declarer would want to discard his losing hearts on dummy's top diamonds; or the missing diamonds might divide 4-3 (62 per cent) when a diamond ruff in hand establishes the suit, all South's spades are discarded and just a heart is lost.

Well, thought South, a 12 per cent edge is a 12 per cent edge so, after unblocking his ace of diamonds, he drew trumps and discarded a club on the king of diamonds. The queen of diamonds, however, brought the bad news. The diamonds could not be established and it was now too late to play for the ace of clubs to be right.

Where did South go wrong? After releasing the ace of diamonds and drawing trumps, he should ruff a low diamond in hand at once. That way, he has not committed himself to either main chance. But now, when the king of diamonds finds East showing out, declarer knows he must rely on the clubs. If East had followed suit then, in percentage terms, the chances of a 4-3 diamond break remain best.