How can you know?

In France, they call a player who permanently hands out gifts to his opponents a Santa Claus (Père Noël). When in defense, he will often let a contract through that was supposed to go down. Will you do better than our Santa Claus against this no-trump game?

Dealer South. E/W Vul

The bidding:

The start of the play: West leads the Spade six to east’s Jack and declarer’s King. The latter than plays the Club three to dummy’s Ace, East following with the nine. Next comes the Diamond Queen, East follows with the eight and South with the five…