An Interesting 1NT

[OliverC]

This was an interesting play hand I played with Paula earlier today:

NS Game, Dealer North

You are South. Partner passes, East opens 1 , you bid 1NT (16-18) and everyone passes. West leads the King and Dummy goes down:

North (Dummy)
  J106
  106
  J9854
  K76

King led

South
  K53
  A832
  AK2
  Q109

You duck the Heart King and the Queen which follows it, but take the Jack at trick 3 when East shows out, discarding a small Diamond (and I discarded a small Diamond from Dummy). How do you plan the play from here?

The question uppermost in my mind was "Did East start with 5 Diamonds or only 4?". I decided I was going to play East for 5 Diamonds and West for a void. With the KQJ in the West hand the position of the!S AQ, Q and Ace was not in doubt, but there was just room for West to have the Jack.

If East started with only 4 Diamonds, I can afford to play Ace, King and another Diamond now, because that clears the Diamond suit and East is endplayed to let me into Dummy. That line doesn't work well when East started with 5 Diamonds, however.

At trick 4, therefore, I led the 10, hoping to encourage a cover by West. West duly obliged and Dummy's King was taken by East's Ace. East went passive now and returned a Club which I won. The position was now:

North (Dummy)
  J106
  -
  J985
  6

South
  K53
  8
  AK2
  Q

I was provisionally placing East with AQx, xx, Q10xxx, Axx, so I tried exiting with the King. East could have caused me some problems by ducking this trick (but I would be okay as long as I cashed my last Club winner before continuing the Spades. They took the Spade Ace, however, and played a 3rd Club, won in hand.

4 tricks to date so I need to find another 3. I again played a Spade to Dummy and the 10 was allowed to hold. Now the Jack of Diamonds forces a cover from East (and West played one, so AK and a 3rd Diamond would have been better as it turns out). I won and exited with a Spade. East could cash a 4th Spade, but now had to lead away from 10x to give me a 7th trick.

All this brain-ache only netted me the princely amount of ½ an IMP (mainly because some lunatic in the West seat had contrived to go -4 in 4 XX), but it was a fun hand to try to work out.