At every table the final contract was 2, 3 or 4♥ by North or South. If South played it, the lead was ♦6 or 8, if North played it, the lead was a top club.
At my table declarer made nine tricks, which look unassailable, but when I looked at the results I saw that the number of tricks NS had made varied between nine (x4), eight (x3) and seven (x1). It looks to me as if the defence have four top tricks, declarer nine, no side has any tricks to establish, no means of discarding losers, so even if the defensive tricks aren't cashed immediately they don't go away. There's no squeeze or trump promotion. How can EW hold declarer to fewer than nine tricks?
Most pairs will play a weak NT so the auction is likely to start 1NT - 2♥ (or Landy or something) - 3♦ (or Lebensohl). The only thing I can think of is that East lead out three rounds of clubs and then won the first diamond with the ace to disguise his count, persuading North to play him for ♠Q, but I doubt that this happened at four out of eight tables.
Can anyone think of a likely answer?