Doubling slams

Let's say you pick up what seems to be my average sort of hand these days:
xx, xxx, JTxx, Qxxx
The opponents bid rapidly and confidently:
1S – 2H; 3S – 4NT; 5D – 7S;
What do you lead?

It's a crapshoot, basically. Assuming the opponents have at least some idea what they're doing, dummy thinks he has a lot of tricks available. Almost certainly, he's counting on at least six spade tricks, and you have no reason to think he's wrong. He did bid hearts, so maybe he has a decent heart suit too. With no clues, you flip a coin and lead a club or a diamond. I'd probably lead a club, myself: if partner can produce the king, we may at least threaten to win a trick later.

Now suppose partner doubles the final contract. What do you lead this time? The classic answer is to lead something unusual. The only unusual lead this time is a heart. It doesn't look very promising from our hand, but maybe dummy is bidding based on a long suit, and declarer has more support than he is expecting. It's just possible that partner is void, and will ruff at trick one. This would be an example of the famous Lightner double. I don't know if it would be a good example, because from this sort of bidding, I would expect there to be a real chance that the opponents can run to 7NT if you double 7S. But perhaps partner feels that the gamble is worthwhile, since they are going to make 7S anyway if he doesn't double.

So far, so not-very-controversial.

What changes if the final bid on the sequence above is 7NT instead of 7S? Now I think the picture of two good suits is a lot clearer. People don't bid grand slams like this unless they can count the tricks, most of the time. I think declarer sees six spades, five hearts, and two aces in his mind's eye, and we're toast. But my original answer stands: flip a coin and lead a club or a diamond, and for me personally, it's probably a club.

Now the tricky one: what if partner doubles 7NT? What do you lead, and why? What does partner have? Is this a Lightner double?

I don't think this can be a traditional Lightner double. All it can mean is that declarer has screwed up at the most basic level, and partner is looking at an ace. If partner has a sure trick in spades or hearts, I don't think it matters what you lead: the contract isn't going to make. If partner has a minor suit ace, though, the lead may be crucial, because declarer may have thirteen tricks if you miss at trick one. So do you flip a coin again? I think so. I don't think a spade or heart lead can be justified, and I don't think there is any clear message from the double.

Partner led a spade, which is always wrong. I was looking at the AD, and mostly doubled just because we were already screwed if the contract made, so the double was “free”. Dummy hit with seven spades, so declarer didn't need a diamond trick. -2490 is a score you don't see too often, thank the gods.