South’s pre-emptive overcall suggests a very long suit. You might wait for partner to re-open with a takeout double, but with two first round controls you decide on an immediate 4S, and partner raises to slam. North leads the eight of hearts to the jack and queen and you ruff. How will you play?
You have eleven sure tricks: seven spades, two diamonds and two clubs. If trump break 2-1 there is a very simple line: draw trump and concede a club, then ruff your fourth club in dummy if necessary. But when you play a trump to the ace South shows out. That means North has J10 of spades, and if you take a ruff in dummy you will establish a trump trick for him. Is there an alternative line?
The obvious course is to establish diamonds. If they are 3-3 you can draw trump, play ace, king and ruff a diamond, then enter dummy with the king of clubs to discard both your club losers on diamonds and make all thirteen tricks. A 4-2 break is more likely, but you can still establish a long diamond on which to discard one club by ruffing twice in hand. That will be fine if North has four diamonds, but if North has the doubleton diamond he will overruff and there will still be a club loser. Can you see a way round this?
You need to preserve dummy’s trump as entries, so play the king of hearts from dummy, and, when South covers, discard your second diamond! If South returns a club win the ace to keep an entry to dummy. Now play ace of diamonds and ruff a diamond – your cunning loser-on-loser play means that North cannot overruff. Finish drawing trump and ruff another diamond safely, then cross to the king of clubs to discard your two remaining clubs on the established diamonds.