Everyone knows what to do when they have a game forcing hand... Open their system's strongest bid. However, what to do with extreme shape hands no one really knows for certain.
This hand from the Llangollen swiss teams held recently caused absolute mayhem at 28 of the 30 tables in play. I know of one North who opened 1♣, one who opened 5♣ and one who passed (!), probably hoping to come into the bidding later with some kind of No Trump call to show the minors.
What happened then? At my table North opened 5♣ and East found a very brave take-out double on what is about an 11hcp hand. I passed and West jumped to 6♥. When this came back to me I 'knew' that 7♣ would probably be a cheap save if partner held 8 clubs or 7 and they remainder broke 2-0 and bid 7♣. Yes, we may have two cashing Aces but... whatever!
This turned out to be a good bid because 7♣X was only one off for -100. At our team-mates table, they were allowed to play in the making 6♠ which resulted in a huge swing for us of +16 IMPs.
When we seen the hand records later it was noticed that a small slam is making in every suit. 6♥/6♠ by East or West, 6♣ by North or South and 6♦ by South. Poor North can only make 5♦. East needs to find the K♣ lead and West must ruff it with his singleton J♦!
The most IMPS to change hands on this deal was when a double slam swing occured. West made 6♥X for +1660 and South somehow managed to play in 6♦ for +920. A total of 21 IMPS swing!
Only TWO flat boards. One where both tables played in 5♣ making and one where both tables played in 6♣X making. Only one constant, everyone who played the hand made 12 tricks! It's a funny old game.