South opened the bidding with 1♣, and I overcalled 1♦. North then bid 4♣, suggesting that he had at least 5 clubs. Surprisingly, my partner then bid 5♦, implying that he held 6 diamonds. South then bid 6♣ (I strongly suspected that he held the void in diamonds and a lot of clubs). Despite being vulnerable, I decided to take my chances bidding to the 'level of the fit' and bid 6 diamonds. Obviously South doubled me.
The layout turned out to be:
So, with hindsight, I was 'correct' to bid 6♦ (we were down 2, costing us 500 points, while the opponents would have made 500+120 points with their slam (drawing trumps, cashing all their hearts and winning ♠A)). However, what should actually have been done in the situation (or in similar situations where you have a weak hand but a massive fit in another suit)?
EDIT: Sorry I forgot to mention that we were playing rubber bridge and NS had earlier made 1♥.