Once a bridge expert said: Do you remember when you used to lead the Queen from QJ alone in trumps? And then you grew a little more subtle and began to lead the Jack. And then an even more subtle declarer realised that the Jack was probably from QJ alone. Until finally you spun a coin as to which to lead.
This of course is the first step towards a ” mixed strategy.” Let us go, however, a little further in this very example. Consider the case where you hold the lone Queen or the lone ‘Jack in trumps. Would that be a good card lead? Obviously, such a lead would be poor, for it frequently presents declarer with an extra trick, as in the following examples:
 10 x x x |
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| Q |
A x x |
|
| K J x x x |
Or
| Q 9 x |
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| J |
K 10 x |
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| A 8 7 x x |
etc., etc.
When you, therefore, lead Q or J from QJ alone, declarer may reasonably infer that you hold the other honour as well. On the other hand, declarer, if left alone with the following layout:
| x x x x |
||
| Q J |
x x |
|
| A K 10 9 x |
will (and should) take a second round finesse, after having dropped an honour on the first round! So, your attempt to deceive the declarer turns out to tell him the truth, while otherwise he would most probably have taken the wrong view. The conclusion is that to lead singleton Q or J is too likely to lose a trick by force, and to lead from doubleton QJ is also mistaken.
There is more than meets the eye in this example. In most situations the best policy does not aim at deceiving the opponent but towards telling the least possible.
Consider this common layout:
| K J x |
||
| Q 10 x |
x x x |
|
| A 9 x x |
the declarer, leads small from his hand, successfully finessing the Jack. When next the King is played from dummy, West should drop the Queen. This is an old chestnut. The intention underlying this move, however, escapes usually most of the players, who believe that they are deceiving the declarer, enjoying their 10 as a great surprise whenever their opponent guesses wrong. In fact the intention in playing the Queen is just not to tell about the Ten. For declarer knows the Place of the Queen, whereas he does not know anything about the 10. So, West tells him about what he already knows. The Queen is not a deceptive card. It is a least a revealing card.
We now can discuss the strategy of this situation, described by Terence Reese:
| A J 9 3 |
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| K Q 4 |
10 8 2 |
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| 7 6 5 |
Declarer leads the 5, West following with the 4 and hoping declarer to finesse the 9. But declarer, Terence Reese says, may make the ” upside down inference ” that, had West held K10x or Q10x, he would have played the King (or Queen) in order to ” deceive ” declarer or at least to give a guess and to make entry difficulties for him.
Hence West’s failure to do so induces declarer to play dummy’s Jack. But should West use this tactic, asks Terence. Of course not! On the principle of the least revealing move, West should always play high, whether he holds K10x or Q10x or KQx.
Or he may always play low. (This strategy, though weaker in regard to entry destroying, is equally good as to the principle of ” least revealing “.)
Once declarer meets a defender behaving according to this principle, his best strategy is simply to follow the greater a priori probability, which is to place West with K10x or Q10x rather than KQx. Thus the defender reduces declarer to his a priori chances, and obviously this is the best he can do in the long run.