The “Positive” Negative Double

After North opened 1NT with the singleton Q of hearts on the first board of the set (apparently had a diamond mixed in with his hearts) the third board brought into play an interesting “positive” use of the negative double – the hand in question was

Dealer:N Vul:E-W	North ♠ 10 ♥ AK76 ♦ A72 ♣ QJ742
West ♠ J9 ♥ J84 ♦ KJ853 ♣ 863		East ♠ KQ632 ♥ Q93 ♦ 10964 ♣ 5
	South ♠ A8754 ♥ 1052 ♦ Q ♣ AK109

The bidding proceeds

There was a  long BIT before the DBL,  an even longer BIT before the 4NT call, and the DBL was explained to West by North as “negative”.

What was South thinking before the 4NT call? Perhaps something like “Well, partner has shown an opening bid, and I have 13 HCP, so maybe we should investigate slam here – we might even have a 7card club fit”. What must North think over 6C? Maybe “Probably best to ignore the (advertised?) eight card heart fit – surely 6C will score better than 6H”.

It goes without saying that 6C is the only slam that makes, and that it was bid by only one pair in the field. Time to switch to “Positive-Negative” doubles methinks.