I was once told that a perfect top is when every table plays the same contract, everyone else scores the same result, and you are the only person to get a top because of something good you did.  I don't ever recall getting a perfect top, but at the club game with Helen last week, I had an opportunity:

Neither vulnerable, Helen dealt and opened 1♣.  Despite LHO's 2♥ overcall, we swiftly located our spade fit and bid to 4♠.  LHO led the ♣6 without apparent thought and dummy came down.  This looked like a normal spot, with both of us having clear openers and a 5-3 spade fit, yet not enough for slam.  I counted no losers in the black suits, but I could lose 4 tricks in the red suits if the cards lay badly. 

I inserted the ♣8, but RHO, a Grand Life Master, covered with the ♣9 and I won the ♣K.  I pondered over whether it was right to steal a heart trick now and hope to pitch the heart loser on the clubs, but the quick club lead concerned me.  In my experience, people do not smoothly lead from three or four small, especially in dummy's first-bid suit, so stealing a heart didn't have much upside and could have some downside.  I eventually decided it would be best just to clear trumps.  Surprisingly, RHO threw the ♥10 (upside-down attitude first discard) on the second round, indicating that trumps were 4-1 originally. 

At this point, I saw no harm in continuing to draw trumps, overtaking the ♠J with the ♠A to throw a diamond from dummy on the ♠10.  RHO discarded the ♣4 and then the ♦10.  With LHO marked with at least 9 cards in the majors, it didn't look like clubs were 3-3.  Sure enough, on the ♣Q, LHO discarded the ♥2, confirming that his quick ♣6 lead was a singleton. 

Here's the current position, with no tricks lost:

How would you continue?

Barring exotic endplays and squeezes, the normal play to hold the diamonds to 2 losers is to lead low to each honor, losing only when the ♦Q is sitting over the ♦J and the ♦A is sitting over the ♦K, approximately 75%.  However, I had a lot of extra information:

• LHO was known to have started with exactly 4 spades and 1 club, and at least 5 hearts for his overcall.  So he was likely 4=5=3=1 or 4=6=2=1 (with 4=7=1=1, he probably bids more, or leads the singleton in his unbid suit, diamonds).
• LHO doesn't need the ♦A to overcall, especially white at MP with 4-6 in the majors.  However, if LHO started with at most 6 hearts, then RHO started with at least 3 hearts.  Let's say RHO holds the ♦A.  With the ♦A to go with his singleton spade and trump support (♠x ♥10xx ♦A10xx ♣J9xxx), he surely would have found a raise to 2♥.  Therefore, the ♦A was on my left, in the overcaller's hand.
• If LHO were 4=5=3=1, RHO would be 1=4=3=5.  Holding ♠x ♥10xxx ♦Q10x ♣J9xxx, most players would have made a preemptive raise.  So LHO rated to be 4=6=2=1 with both red aces.

I didn't know who had the ♦Q, but I didn't care.  I led a low diamond from hand.  If LHO had both ♦AQ, he would have to win and then I could establish my ♦KJ for a trick.  However, LHO followed low, and RHO won the ♦Q.  He returned the ♦9, but I ducked, playing the ♦7.  As I suspected, the ♦A popped up on my left, so I had 10 tricks (5 spades, 3 clubs, and a trick in each red suit) for +420.

At game's end, I looked at the traveller.  Everyone was in 4♠, but to my surprise, I was the only declarer who made it.  Probably most went down taking the normal line, but a strong player told me what happened at his table.  In an attempt to misdirect his opponent into thinking he held ♥Qxx and preserve overtrick chances, he led a heart at trick 2.  The ♥K won and then play proceeded exactly as it did at my table.  But now, in the endgame, he could not lead a diamond to the ♦J like I did.  With no heart stopper left, the defense could win the ♦Q and lead hearts to tap him out of trumps, and then use the ♦A to cash hearts.  The trick 2 decision did matter after all!

So, my first perfect top, right?  Alas, another pair managed to go down 2, so everyone else didn't score the same result!  Some other time...