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  S: x x x
  H: K T x x
  D: J x
  C: A Q x x
 S: K x x 3 
 H: 9 x x 
 D: x x x 
 C: J x x 
DEALER  S: Q J x 2
 H: A 8 x
 D: Q x
 C: K 8 x x
W
E
S
T
41E
A
S
T
SOUTH
  S: A x
  H: Q J x
  D: A K T x x x
  C: T 9

West       North      East       South
T Tahseen  Oxonian 1  T Kenney   Oxonian 2
            p          1NT        2D
 p          2H         p          3H
 p          4H         end
A board to give me nightmares for years

Let's start by putting the hand in context; you're playing for Cambridge B against Oxford B in the Portland Bowl semifinal, it's the last stanza and you're 16 IMPs down. So far this stanza you've beaten a cold-off game that seemed plausible to find, held 1NT tight, and missed a cold grand slam (qv).
You are sitting East and the aution proceeds as shown. It looks like declarer may have some diamond tricks so you lead the queen of spades to set up winners. Declarer wins dummy's ace, partner playing an encouraging three, and runs the queen of hearts. You let this hold and declarer switches to a low spade (continuing trumps would be better). Partner is on the ball and rises with his king to lead a low club through (though the jack would make life easier). This goes to your king and you continue the suit to remove declarer's entries to hand. Declarer now ruffs a spade and leads the jack of trumps from dummy, which you take. This is the position:

     ---
     KT
     Jx
x    Qx    x
9          8
xxx        Qx   
x    ---   8x   
     ---
     AKTxxx
     ---
If declarer can get to hand, he can draw the last trump and win diamonds, so I must lead a diamond. Unfortunately, I am endplayed in diamonds to set up declarer's jack. However, this is one of those fairly common positions where leading the queen causes the jack to block the suit, preventing a third diamond trick. Alas, I failed to notice this at the table, and lead a low diamond. We lost the match by one IMP!

At the other table, 4H was allowed to make with an overtrick. The play is not instructive...