This hand is from the 2000 Olympiad in Maastricht.

10 7 5 4 3 2
--
A Q J
A K J 8

With both sides vulnerable you are in 3rd seat and after 2 passes you open 1. LHO jumps to 3 and your partner cue-bids4 to show a good spade raise. RHO bids 5 and it's up to you.

There is no scientific answer, but I think that a jump to 6 is practical. Partner must have some of his values in spades, so we hope we won't have 2 trump losers.

The K is led and this is what you see:

A K J 6
10
10 8 3
10 9 5 4 2

10 7 5 4 3 2
--
A Q J
A K J 8

You ruff, of course, and when you lay down the A everyone follows. What are your chances of making this contract?

At first glance, you might go down if you lose to both the K and the Q.

However, there is an almost 100% line of play available. Simply draw the other trump and play a club to the ace. Once everyone follows, you can guarantee our slam (even if West had shown out, you'd still be cold).

Cross back to dummy in trumps and lead another club and finesse your J. If it wins, you have no club loser. If it loses (clubs were 2-2), West is endplayed. He has to either give a ruff-and-sluff, or break diamonds. In either case you can throw your other diamond on the 5th club, and won't need the diamond finesse.

This was the full deal in Maastricht:

Vul: Both Dlr: North	A K J 9 10 10 8 3 10 9 5 4 2
9 K Q J 4 3 2 K 6 5 4 2 3		Q 8 A 9 8 7 6 5 9 7 Q 7 6
	10 7 5 4 3 2 -- A Q J A K J 8

West	North	East	South
	Pass	Pass	1
3	4	5	6
Pass	Pass	Pass

If declarer carelessly cashes the AK first, he goes down. He'd lose to the Q and the K. Starting with the diamond finesse might work, but only because declarer would get lucky. He could test diamonds before playing clubs; when West shows up with 5 diamonds, to go with his known 6 hearts (from his preempt), declarer would know to play East for the Q.