EAST opened 1H, planning to rebid in no-trump unless West responded in spades. When he did the first priority was to show support, so East raised to 3S and West bid game. North led a club, and declarer was happy to see the queen score. He could now count four tricks in the minors, the ace of hearts, five trump (even on a 4-0 break cashing the king first allows him to pick up Jxxx in either defender's hand) and a club ruff in dummy. That was a comfortable 11 tricks, but the event was match pointed pairs where a 12th trick would be worth extra points.
After drawing trump in two rounds declarer cashed the ace of clubs, crossed to the ace of diamonds, ruffed his third club, then played king of diamonds and ruffed a diamond to eliminate these suits from his hand and dummy.
Then he played the jack of hearts. North saw the honour – and covered it. Declarer won the ace and led a heart towards his 10x for that elusive 12th trick.
It is technically wrong to cover the first of touching honours. If the jack of hearts is allowed to run to the king South can return the nine through the 106 and the defenders make two tricks rather than one. If the J10x of hearts were visible in dummy the defence would be easier. As it is North should ask himself why West is leading the jack: unless he has a second honour the play makes no sense.