This is the last of three exercises following the article 'Ruffing: sometimes it's good... but sometimes it isn't ***, which has been published earlier.
To read that article, click Ruffing at bridge play.
For exercise 1, click: Ruffing at bridge play- Exercise 1.
For exercise 2, click: Ruffing at bridge play- Exercise 2.

S/All		♠	Q 10 8
		♥	8 5 4
		♦	Q 7 6 5 2
		♣	10 3
		♠	A K J 9 5
		♥	A 3 2
		♦	A K 10 8
		♣	A

¹ Game forcing
² Relay
³ Weak, but not North's weakest possible bid, since instead of 4♠ he could have bid 3♣ (second negative), raising to 4♠ next: this way he would have promised a bust
⁴ See ³: North shows some strength, so South takes the plunge

West leads the ♣K.
How should South play?

Solution

A non-observant declarer will not spot the problem before it's too late: the diamond suit is blocked.
Suppose declarer, after winning the lead with the ♣A and drawing trumps, starts on the diamond suit. If it turns out to be 3-1 (the most common distribution) and the ♦J is in the three-card suit (biggest chance)...

S/All		♠	Q 10 8
		♥	8 5 4
		♦	Q 7 6 5 2
		♣	10 3
♠	7 6			♠	4 3 2
♥	Q 10 7 6			♥	K J 9
♦	J 9 4			♦	3
♣	K Q J 9			♣	8 7 6 5 4 2
		♠	A K J 9 5
		♥	A 3 2
		♦	A K 10 8
		♣	A

...declarer has to play the three top honours in order to pick up the ♦J. After that South is left with the bare master diamond (either the ♦10 or the ♦8) and North still has the ♦76. The fifth diamond trick (and the twelfth trick in all) has just flown out of the window.

Declarer can solve this problem by, after winning with the ♣A, drawing three rounds of trumps, ending in dummy. Next he plays the ♣10, discarding a blocking diamond from his hand. Now he can cash five diamond tricks without encountering any problems, on the assumption that suit is not 4-0. South then pitches his two heart losers on dummy's fourth and fifth diamond.

Declarer cannot complain about his luck: if West had led a heart, 6♠ wouldn't have stood a chance. Not a nice result with 7♦ on ice...