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Scoring: Matchpoints
Board 4 Traveller
Perhaps my inexperience got us into a bad contract, or maybe this was just a misfit hand.
After losing to the A♥, trumping a heart trick, and then pulling 3 rounds of trump, GiB plays low to the A♦.
Then, GiB decides to use its last trump on dummy's 6♥, cash the K♦ (the Q♦ drops) and continue with the J♦. West trumps, and now GiB has no way to get into its hand to win the 3 remaining diamonds.
Clearly, the GiB decided to play for the Q♦ to drop (which worked) instead of going for the finesse.
However, I'm not sure why it felt the need trump dummy's 6♥, and lose trump control, instead of continuing to play diamonds and discarding the 6♥ later.