A deal from a recent duplicate at Cheadle Hulme Bridge Club.
After the above auction North, with an unenviable choice, led a small spade. West won and returned a spade, again ducked by North while South discarded the three of diamonds showing standard count. A third spade was now played to North's ace while South discarded the three of clubs. North now cashed the ace of diamonds felling declarer's king. North can now deduce that declarer's distribution is 5215 and that South must have the ace of hearts to be able to beat the contract. However North would like a club ruff as well to beat it by two tricks. North should play the heart king followed by the heart two. When South wins this with the jack he has a count on the heart suit and also knows that West is 5215 or 6214. In the latter case North would have a singleton club which he would have led initially, so North must have a void club.
Although this deal is an example of good cooperative partnership defence, perhaps the most remarkable aspect of it is that North South can make a grand slam in diamonds, with a fair amount of good fortune. Six diamonds is a fair contract and five diamonds excellent yet all tables played in spades by West at some level.
Thanks to John Currie for the analysis of this deal