Jack in the Box by Foxymoron

The jack playing card goes back a long way. The knave of coins stems from the turn of the 14th century. It changed from knave to jack in the 19th century. and other names have included lancer. The jack-in-the-box is also very old, from the fifteenth century, and was a popular child's toy. Finding out how the jack popped out was part of the fun.

Finding the knave was the theme of an interesting slam last week. Usually when you are missing five cards including the knave, you play out the ace, king and queen. But not always:

West opened 4C at one table, which was very sensible, and North doubled. South had quite a bit and jumped to 5D, and North decided to bid a sixth and 6D was the final contract. This was a bit pushy but not unreasonable. West led a top club and switched to the king of spades. Now declarer won, cashed the queen of diamonds, and had to decide whether to finesse on the second round. Assuming the clubs are 8-2, then we can calculate the odds for both plays. West has five vacant spaces in which the jack of diamonds might be lurking and East has 11, so the finesse is slight favourite.  And even if West does have two diamonds, East can still have the jack. It is very close, but the "right button should be pressed" and the jack would pop out. It is not good enough to play two top diamonds before finessing, as you need a trump in dummy to ruff a club.

The observant reader might notice that Six Diamonds can only be made by North, not by South. That puzzled me for a while. The king of spades is no good as a lead but a low spade is the key to the box. If declarer wins with the ace and draws trumps and throws clubs on the long hearts, there are still two spade losers. The king of spades does not work as a lead because declarer draws trumps, throws clubs on the long hearts and gives up a spade. And played by North there is no way to stop declarer opening the jack in the box.

And apologies for the lack of any blog for a while. Other projects were on the go.