A defensive problem from the Corwen Trophy earlier this month.
Non-vul vs Vul. Matchpoints Dealer South
After a very short auction you lead the diamond ten which declarer wins perforce in the dummy. He then plays a spade to partner's jack the six and your two.
Partner plays the five of hearts to declarer's ten, you win with the jack and return a spade to partner's king, declarer following with the eight. Partner continues with the six of hearts, declarer tries the king and you win the ace and play another heart to partner's queen and declarer's two. Partner now plays the eight of clubs to your ace declarer playing the six. This contract is already two off, what now?
If partner started with the jack doubleton of diamonds and is awake you can promote your nine of diamonds by playing the spade ace for partner to trump.
At the twenty five tables where this deal was played in diamonds no-one found this defence, though declarer's line of play may have made it more difficult for the defence to find the right sequence of plays.