I sat at South. They played Acol strong 2♦ opening. My partner passed (If I were him I would preempt 3♠ here). RHO responded 2♥ showing value in ♥. I doubled asking my partner to bid an unbid suit as I had great offensive value but lacking defensive value.
The opener raised to 3♦, partner overcalled 3♠, confirming a ♠ fit. RHO responded 4NT.
I now think that they were likely to have a slam in ♦ and bid 5♠ to disrupt their bidding, hoping that they would double us instead of bidding 6♦ themselves, but they really bid 6♦ themselves. Their slam is definitely makeable and I believe I should make a sacrifice to 6♠ to have better result, but it resulted the opener to bid 7♦ which my partner doubled. The result was solid 13 tricks by them, 7♦X= by West.
Par contract was 7♠X-4. Among the 7 tables, 5 ended up at 5♠ by north (4 were doubled), 1 ended up at 5♦, that meant at the moment the 6♦ was bid we were doomed.
Was we unlucky at this board that they could bid slam? If North instead preempted 3♠ over strong 2♦ opening, would it be less likely that they could bid slam? (If North preempted 3♠ I would bid 4♠ over anything and ready to compete to 6♠ having 12 trumps)
mikl_plkcc's deal. MP scoring.
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Just unlucky. North could overcall.
South might prefer some other action to a double.
With hindsight, It's easy to criticise South's competition to 6♠ but it looks fine to me.
A imps, over 7♦, North should probably "bid one more";
but at MPs, pass/double seems reasonable.