This deal has a special vividness for me, as I had a tooth removed yesterday and during the lengthy extraction (took three dentists in the end, all taking turns) I tried to recall every detail of the hand, to distract myself. Here it is:
I've starred the conventional bids in the auction. South had an easy 1♥ opener, playing five card Majors. North replied with Jacoby 2NT, agreeing Hearts as trumps and game forcing. East (Sabine Auken) then came in with 3♣, natural. Over this South was able to make his usual bid of 4♣, a splinter showing a singleton or void Club. West (Roy Welland) found a nice bid over 4♣, bidding 4♦. As a passed hand this must promise Club support (enough to play at the 5 level), but also shows some cards in Diamonds. North knew partner had an opening hand, with nothing in Clubs, so could presume a Diamond control and bid 4NT as Blackwood. South has a void and and 3 keycards. For me and Anna, that would mean bidding the void suit at the 6 level (here 6♣), or 6 of the trump suit if the void is above trumps. This North-South had a different agreement though, or forgot their agreement, as South bid 5NT. I wonder if they did get muddled, as North then signed off in 6♥, whereas if you know you've got all the keycards you could look for a Grand Slam, presumably by bidding 6♦ and hoping partner realises you're worried about Diamonds and should bid 7♥ with the King of Diamonds.
6♥ was an excellent contract, making if either the Diamond finesse is on or you find the Spade Queen. Because East has shown long Clubs in the auction, I think finessing Spades is better than playing for the drop, but there is in fact an even better line.
Here's what you do. First ruff out the two Clubs, draw trumps, and cash the ♠A. Then, you play a Spade to the King. If Spades are 2-2 and the Queen drops, you're home. If it turns out East has the Queen, you have to rely on the Diamond finesse. But if it turns out West has the Queen, you're in business. You now give up a Spade to West. West only has Clubs and Diamonds left, so must either lead a Club and give you a ruff and discard (that's why you had to ruff out the Clubs earlier), or lead a Diamond round to your Ace-Queen. Playing it this way is better than just a straight Spade finesse, as you make it when the Spade finesse is on and also when the Queen drops.
At the table declarer mistimed it. She followed the line above, but forgot to ruff out the Clubs early on. When she decided to ruff out the Clubs she had no easy entries back to dummy, so had to use up an extra round of trumps getting back and forth. That meant by the time she lost a Spade trick to West she no longer had a trump in each hand, so West could play a Club without giving a ruff and discard.
Final result then was 6♥-1. On the other table after a 1♥ opener North replied 1♠, instead of a Jacoby 2NT. This made the North-South auction much harder, as South didn't know partner had a trump fit or an opening hand. North-South ended up playing 4♥+2, the wrong contract but it gained them IMPs here.