[mamos]

Please don't criticise NS bidding - that's a whole different story

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I was South, my partner - a good friend and a favourite partner.

I lead ♦K. Our agreement is A for attitude (reverse) K for count (standard)

Play to the first trick is shown.

My partner believes the ♦Q is the correct card to play. I favour the ♦5. I think that I was taught that the Queen here promises the ability to win Trick 2 in Diamonds. I lead ♦10 at Trick 2. (Suit preference for Hearts). Not surprisingly the ♦J won the trick. (Well it was surprising to me!)

I am unable to find any evidence for my recollection that the Q should imply that partner can win the next trick and as ♦J is in dummy it must be a singleton. I would be gratful for opinions and ideally documentary confirmation.

Mike

[Cyberyeti]

You are right I believe, you play low from Qx unless you have the J and think it's standing up. If dummy has the J you also play low, partner is entitled to think you're ruffing the next one rather than gratuitously giving dummy a trick.

[FelicityR]

Third hand plays low

But all seriousness, partner is not expecting you to have 6♦s...

I don't quite understand the lead of the ♦10 at trick 2 if you are thinking the ♦Q is singleton. That gives declarer 3♦s in his hand...

However, to be perfectly honest, sometimes it would be right to peter with a doubleton Qx, and sometimes it would not. If my partner leads from AK against a suit contract I tend not to waste the Q on the first round holding a doubleton Qx except - as your partner did - I could see a way of defeating the contract.

[nige1]

Mamos: Please don't criticise NS bidding - that's a whole different storyI was South, my partner - a good friend and a favourite partner.I lead ♦K. Our agreement is A for attitude (reverse) K for count (standard)Play to the first trick is shown.My partner believes the ♦Q is the correct card to play. I favour the ♦5. I think that I was taught that the Queen here promises the ability to win Trick 2 in Diamonds. I lead ♦10 at Trick 2. (Suit preference for Hearts). Not surprisingly the ♦J won the trick. (Well it was surprising to me!) I am unable to find any evidence for my recollection that the Q should imply that partner can win the next trick and as ♦J is in dummy it must be a singleton. I would be gratful for opinions and ideally documentary confirmation.
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♦5 is right . ♦Q with a singleton or ♦QJ.. It's rarely right to signal with a potential trick.

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[FelicityR]

nige1, on 2020-July-31, 08:11, said:

It's rarely right to signal with a potential trick.

Precisely. But even I am forgiving your partner for trying to make a spectacular play to try to defeat the contract on this occasion.

[Tramticket]

What do you do if North plays the 5, which you can read as his lowest card? Do you play north for QX or a singleton and under-lead? Wouldn't north encourage with a doubleton in a suit contract - particularly as North will expect declarer to hold at least three diamonds. So, do you carry on with the king when you see the 5? Or switch?

For what it's worth, I would have led the king with your agreements.