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

¹ Quantitative: 'partner, pass holding a minimum; if not bid 6NT'

West leads the ♥J. How should South play?

Solution

Declarer counts nine top tricks.
Suppose he begins by playing the ♣AK.
- If the ♣Q shows up (a better than 53% chance), there are three extra tricks in clubs, meaning he is home and dry. The finesse for the ♠K can yield the overtrick.
- If an opponent has three clubs to the ♣Q, or if West has all four clubs, declarer can set up two extra club tricks only (by playing another club). In that case he will have to hope for the ♠K to be with East. The extra chance of success is 21%.

So by beginning with the ♣AK - which is what most players will do - declarer's overall chances of success are a little over 74%. 
Most of the times these players will get away with it. But not this time:

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

West shows out on the ♣A! Declarer cannot set up even one extra club trick without losing two...
The deal looked so easy from the start. That is exactly the kind of deal where declarer should take a closer look, in order to allow for bad distributions.

There is nothing to lose by starting with the spade finesse, unnatural as it may look. Two things can happen:

1. The ♠Q wins (as here). South can afford a club loser now! Therefore he can afford a safety play in that suit: he plays a small club from his hand without cashing a top club first. Unless West wins with the ♣Q declarer inserts dummy's ♣J. The rest of the deal plays itself: in this case West shows out and East wins with the ♣Q (by ducking East only helps declarer). Later declarer takes the marked double finesse over East's ♣109, having enough entries in dummy.
(Declarer can also execute a different safety play by beginning with a small club from dummy and covering East's card cheaply - meaning he plays the ♣7 if East plays the ♣2 - which East should! Of course West will win the trick most of the time, but then the suit is 3-1 or 2-2, no problem. If East shows out on the first club, South wins with the ♣A and plays a small club towards the ♣J. If East were to insert a higher club than the ♣2 in the first club trick, declarer would win and, on seeing West show out, would proceed to lose one club trick only).

2. If the spade finesse fails (unlike here), South cannot afford a club loser. He takes his best chance not to lose a club and set up two (in fact three) extra club tricks by playing the ♣A and the ♣K from the top.

The idea behind this line of play - which adds an extra 2.4% to his chances of success, bringing his total to 76.6% - is that declarer can only afford a safety play in clubs if the ♠K is with East. Therefore he begins with the finesse.