Opening lead: 
3.
Bidding commentary: South’s jump rebid to 3
is invitational. Think of it as showing a reasonable six-card suit with 9-11 high-card points.
Lead commentary: In the absence of anything brilliant to lead, the unbid suit is usually a sensible choice.
Play commentary: South might just as well play the king from dummy at trick one. Every so often, an ace is underled through a dummy that has shown strength.
Defensive commentary: Given the lead, West cannot have more than five diamonds, which means South has at least three diamonds. Furthermore, West is marked with the jack given declarer’s play of the king at trick one. If declarer had the J, he would have played low from dummy. Also, the lead of a low card strongly suggests an honor, and the only honor missing is the jack.
Defensive commentary #2: Considering what East knows, he should play three rounds of diamonds, forcing dummy to ruff. Once dummy ruffs, West has two trump tricks as declarer can lead hearts from dummy only once.
Play commentary #2: If the defenders do not play three rounds of diamonds, a diamond can be discarded on a spade and hearts can be led twice from dummy, limiting declarer’s heart losses to one trick.