The bidding: South, with 13 HCP’s, opens One Club, and West overcalls One Diamond. West could be a little stronger for a vulnerable one-level overcall, but his suit is so good and often the One-Diamond overcall causes confusion.
The confusion is caused if North bids One Spade, which he will, and partner thinks it is five cards. In competition, this is usually correct except in this case. A One-Spade or One-Heart bid shows four cards or more, and a double shows exactly four-four in the majors.
Even though East has tolerance for Diamonds, he will not overcall Two-Hearts because the Heart suit is really poor. It could easily be a three-loser suit and possibly a four-loser suit.
South cannot bid One No Trump as he does not have a Diamond stopper. Each time any No Trump is bid after opponents have bid a suit, one stopper is shown. So if each player bids No Trump, each has a stopper. So if one player bids No Trump twice, he has two stoppers or enough tricks ready to run.
This is the second case when one rebids a minor with five cards. Normally rebidding a minor shows six cards.
The Play: West leads the Diamond King which East overtakes and leads back his other Diamond. West continues the suit because Dummy still has Diamonds, and he wants to shorten the long-trump hand.
West does not lead his singleton Heart because he has a natural trump trick.
Declarer ruffs the third Diamond, takes the heart finesse which East wins and returns the Heart Ten. West refuses the ruff and declarer cashes the top two clubs and then cashes the remaining Heart honour, ruffs a Heart, ruffs two diamonds using all of his trump. Declarer will get six Club tricks, two Spades, two Hearts and no Diamonds, making Two Clubs plus two for +130.