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

¹ Pre-emptive
² Negative

West leads the ♦A (East the ♦10) and continues with the ♦Q. How should South play?

Solution

Declarer has lost one trick and counts two more losers in the ♥K and the ♣K. Totalling three: no problem therefore?
Wrong: East's ♦10 was probably a singleton (remember the bidding?). If declarer, in 'auto-pilot mode', plays the ♦K in dummy in trick two, East will ruff and play a heart. If both the ♥K and the ♣K are wrong, the contract is doomed.

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

Declarer can avoid the loss of neither a second diamond trick nor the ♣K (if it is with East). But he can avoid losing the ♥K.
He does so by not going up with the ♦K in trick two.
- If West wins the second trick, there is no danger since he cannot attack the heart suit. South thus retains the ♥A. He wins any lead by West, draws trumps and finesses in clubs. East wins and switches to a heart but South goes up with the ♥A and pitches the ♥Q on a good club.
- If East ruffs his partner's ♦Q in order to switch to a heart, South wins with the ♥A, draws trumps, crosses to the ♣A (!) and pitches the ♥Q on dummy's good ♦K.

The lesson of this deal is: switch off that autopilot; it is only useful in planes.