[lamford]

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A complex relay auction led to the poor contract of 7NT here, and West led the T♥. It seems that South thought North was showing the QS and North thought he was denying it. If you play a spade at trick two, West will play low. What now?

[smerriman]

lamford, on 2022-January-21, 18:19, said:

and West led the T♥.

You mean East, right?

If West has QJx of spades, they can guarantee beating the contract by playing high. So you assume they don't have that which means your only hope is to drop the QJ offside.

But then West knows you know that, so will play low from QJx so that you fail in those cases after all.

But you know West knows you know that, so..

.. if I calculate right, I think West's best strategy is to play low 1/3 of the time they have QJx, and then it's a coin flip for South.

[steve2005]

South hasn't shown anything about their hand other than having 16+ hcp.
That is an advantage of playing relays, the defense knows nothing about declarer's shape.
So, it isnt automatic for west to play an honour from QJx

So, it is just a matter of determining the odds of west having QJx vs the odds of east having QJ doubleton.
Note: you are down on all 4-1 or 5-0 splits.

I think the odds are the same to be QJx as QJ doubleton, so take your pick

[smerriman]

steve2005, on 2022-January-21, 19:37, said:

South hasn't shown anything about their hand other than having 16+ hcp.

Based on the auction, North is declarer. But the OP also says West led; I'm guessing that's the more likely error..

[sfi]

If North really is the declarer, not splitting with QJx in spades is a bad play with no upsides apart from whatever you gain from a Grosvenor. So you play for QJ tight offside. If South is the declarer, splitting is far from obvious. In this case, the odds of QJx in West vs QJ in East are 3-1, and I think West would duck more than 1/3 of the time. So try the S10.

[steve2005]

smerriman, on 2022-January-21, 19:39, said:

Based on the auction, North is declarer. But the OP also says West led; I'm guessing that's the more likely error..

hmm. either a lead out of turn, or North's first bid was 1♠
or maybe the final contract is 7♠

[LBengtsson]

The percentage play is ♠10 as finesses win 50% of the time

But with two honours out I guess that comes down to 25%

Finding ♠QJ doubleton is less chance.

[johnu]

lamford, on 2022-January-21, 18:19, said:

A complex relay auction led to the poor contract of 7NT here, and West led the T♥. It seems that South thought North was showing the QS and North thought he was denying it. If you play a spade at trick two, West will play low. What now?

The auction says East is on lead, so West has perpetrated a nice Grosvenor Gambit by giving declarer a chance to make by misdefending.

[lamford]

johnu, on 2022-January-21, 23:45, said:

The auction says East is on lead, so West has perpetrated a nice Grosvenor Gambit by giving declarer a chance to make by misdefending.

Sorry, had a typo in the auction. 1H was FG with spades, and South was declarer. So, yes West does not know that South has a singleton spade. I think smerriman's strategy is close, but there are complications.

With QJx, West has to split if South has one spade and play low if South has three spades. If South has 2, anything works, as South would play for spades 2-2 ...

[mikeh]

Incidentally, if west has Qx or Jx he should play his honour, presenting south with a losing option should he hold xx.

Which means that if he splits from QJx, gambling that south has a stiff, it’s far from clear that south should get it right when he has xx.

From south’s point of view, the Jack or Queen should be as consistent with 2=2 as with 3=1, if south has 2, so I disagree with the statement that ‘anything works’ if the suit is 2=2.

Edit: of course, while imo an honour ought to be automatic from Hx on this hand, few defenders even think about that play, so that complicates matters as well.

[steve2005]

When this was posted on bridgewinners Split Decision (bridgewinners.com) south also has Q♣
This makes things a lot better as now there are squeeze opportunities.

[lamford]

steve2005, on 2022-January-22, 09:27, said:

When this was posted on bridgewinners Split Decision (bridgewinners.com) south also has Q♣
This makes things a lot better as now there are squeeze opportunities.

Yes, I removed that to concentrate on the play in the spade suit for this article. Both are interesting of course!