Here's an intermediate thought process ...
Declarer has shown probably about 23+hcp semi-balanced. We know he has 2 clubs, and likely has at least 5 hearts. So shape should be 2-5-4-2 or similar. Partner played 4
♥. If this is singleton or from 42 doubleton, declarer has 6 or 5 heart tricks and is home. So we have to hope p has A
♥ and has held it up, hoping we could win to lead a diamond. If declarer has AK
♠ and thought the contract was in danger from diamonds, he'd probably cash spades first. Also, declarer has made no attempt to set up spades while he has entries to dummy, so either doesn't need spade tricks, or more likely has a holding that guarantees an entry like Axx. Giving partner A
♥ and K
♠ doesn't leave much room for high diamonds, maybe K or Q but not A, and if declarer is 3-5-3-2 partner will be 1-2-6-4 (note that this can be consistent with lead of
♦6. So we may need to avoid telling declarer that partners spade honour is singleton.
Now, what tricks does declarer have? 4 clubs, 2-3 diamonds, at least 2 hearts, several spades - can't see how we're going to beat this ... ok it's MPs, let's try and save overtricks. If assumptions so far are correct (though remember they were based on trying to defeat contract) I need to keep all the hearts so that my ten is a stopper. Similarly if p has a spade honour my ten may be a stopper if I keep all spades. What does p need to know about my hand? Well he knows from counting hcp that I have none, and I can't see how showing length will help him (though it may help declarer). So I'll throw 8
♦, wait for declarer to finesse spades into p's singleton K and watch p cash AKxxx
♦ to punish declarer for being greedy
Robert