This was a genuine and lively board from the Gainsborough Cup, a London interclub event. West tried to cash the ace of diamonds. East playing the five, but South ruffed and led a spade to dummy. I did the best I could as East by discarding the king of clubs, but declarer cashed two rounds of hearts ending in dummy and played the four of diamonds. I underplayed this with the two, but declarer needed me to be 0-2-10-1 so he discarded a club and then ran the trumps squeezing my partner in the rounded suits for +1660. We lost the match on a split tie. I thought my partner should have started with a low club; he thought I should have bid 5NT, suggesting that he underled his AC, instead of 6D. In the other room, South did not find the heart lead against 6Dx so it was quite an expensive board.
Who was to blame, or was it just bad luck?