[ron]

Playing against Meckwell, I opened a strong NT with a 17 count and got to play 4S. At trick 11, everyone was down to only clubs (I had discarded a small one earlier). I had Txx in dummy opposite Qxx in my hand and Meck on my right put a club x through. What would you play?

[adhoc3]

Put myself into that table... hmm... Meckwell is Meckwell, I can't change that... ♣x, to take my 50%.

[ron]

I think I stated this in a poor way, so that the problem becomes too hard. Let's just say I have T32 opposite Q54 and dropped my cards face up on the table by mistake.

[FrancesHinden]

Yes, now it's clearly right to play the Queen.
It's more interesting when there are things such as the 7 in dummy.

[han]

So what happened at the table Ron? Did you play the queen only to find out that Meckstroth mistakenly played low from HJx? If so, can we call this a Grosvenor coup and did it pay off for them later in the match?

Good luck the rest of the championships!

[ron]

Heh, actually I didn't play this against Meckwell, or anyone else. I just wanted to imply that the defenders could be relied upon to make the correct technical plays, without saying so explicitly. I thought it'd be more interesting as a realistic problem but really it's best to think of it in the abstract, as a 12-card bridge problem. For those who replied... are you sure your answer is correct?

[FrancesHinden]

Dummy has 1032, hand holds Q54 and RHO is on lead and plays a small club.
Let's suppose we know that both RHO and LHO have at least 3 cards in the suit, as in the problem you have given us.

All x's are bigger than my x's
RHO can have
AKx (x3)
AJx (x3)
KJx (x3)
Jxx (x3)

Axx (x3)
Kxx (x3)
xxx (x1)

(or AKJ, which is now impossible)

For the last three of these it doesn't matter which card we play.
For the first of those we need to play the queen.
For the other 3 we need to play low, but then RHO has played a technically incorrect card as he had three tricks by force.

Now, you can argue that some of the time RHO has one of holdings 2-4 he should switch to a low one, otherwise we will always make a trick when he has AKx because we'll always rise.

So suppose those first 4 holdings are all equally likely, and suppose he always plays a low one from AKx and plays a low one with probability p from the other 3.

We play a low one with probability q and the queen with probability (1-q).

From RHO's point of view he will take 3 tricks
q/4 + 3(1-p)/4 + 3p/4*(1-q) of the time, or
q/4+3/4 - 3pq/4

So to maximise his trick taking potential he should make p=0, independent of q.
Therefore we should always play the Queen, because he'll never play a low one from HJx.

It's getting late and I've drunk too much wine. Tell me where my algebra has gone wrong. (I was expecting to find he could switch to a low one any time up to a 1/4 of the time without costing his expectation. But I didn't.)

[Blofeld]

FrancesHinden, on Oct 29 2005, 04:06 PM, said:

From RHO's point of view he will take 3 tricks
q/4 + 3(1-p)/4 + 3p/4*(1-q) of the time, or
q/4+3/4 - 3pq/4

So to maximise his trick taking potential he should make p=0, independent of q.
Therefore we should always play the Queen, because he'll never play a low one from HJx.

Your algebra's fine, Frances, but there's a small error in the interpretation: while it's true that trick taking potential is maximised with p=0, independent of q, if p is anywhere between 0 and 1/3 then our opponent will always do best with q=0, so as long as the declarer follows the best strategy (of always rising with the queen) it costs nothing to the defence to underlead holdings 2 to 4 anything up to a third of the time.

There might even be a psychological advantage in doing so.

[ron]

If LHO has AKx, you make a trick by playing low. If RHO has AKx, you make a trick by playing the queen. These are the only relevant holdings, and since they are equally likely, it doesn't matter what you play. Kind of neat, and somewhat unintuitive.

[Chamaco]

ron, on Oct 29 2005, 11:13 PM, said:

If LHO has AKx, you make a trick by playing low. If RHO has AKx, you make a trick by playing the queen. These are the only relevant holdings, and since they are equally likely, it doesn't matter what you play. Kind of neat, and somewhat unintuitive.

One might consider inferences from the opening lead: if the opening leader did not lead a suit headed by AK, more often than nor h should have good reasons not to do so.

When there are no clear evidences from the bidding that would have discouraged him to lead that suit, I believe it is a fair assumption to TRY and hpe that his partner might have AK in the suit, no ?

[mr1303]

In terms so simple that Mike Bell (MickyB) can understand it, what is a Grosvenor Coup?

[FrancesHinden]

A Grosvenor Coup is when somebody makes a play that costs a trick, but it's so stupid that the other side then lose that trick anyway.

The original example, where Lord(?) Grosvenor was East, was something along these lines (I've completely forgotten the hand, but the concept is correct)

J10xxx
-
Axxx
Axxx

AQxxx
AKQxx
Kx
x

South is declaring 7Sx on a heart lead, ruffed in dummy with the Jack on which East discards. South now tries to drop the singleton SK in the West hand, as East clearly cannot have it, and discovers that East had Kx all along.

It has no benefit to the defence other than making East cross.

[pclayton]

FrancesHinden, on Nov 3 2005, 02:16 AM, said:

A Grosvenor Coup is when somebody makes a play that costs a trick, but it's so stupid that the other side then lose that trick anyway.

The original example, where Lord(?) Grosvenor was East, was something along these lines (I've completely forgotten the hand, but the concept is correct)

J10xxx
-
Axxx
Axxx

AQxxx
AKQxx
Kx
x

South is declaring 7Sx on a heart lead, ruffed in dummy with the Jack on which East discards. South now tries to drop the singleton SK in the West hand, as East clearly cannot have it, and discovers that East had Kx all along.

It has no benefit to the defence other than making East cross.

John Swanson wrote an article that attributed the coup to Frederick Turner.

I think Grosvenor is a fictional person.

[Kalvan14]

Was that the article posing that Turner might have been killed because he was obsessed with Grosvenor coups, and was always playing to set up them?