It's taken a play problem to get me at least partially out of my brief hibernation.
I win the lead, cash the spade K. If the 10 drops then the play is (close to) trivial and I won't expound further.
If LHO shows out, I play for an elopement: I will cross in clubs to advance the diamond Q. I am not down (yet) even if this loses, tho I am much happier if the diamond K is onside. I won't elaborate further.
If RHO shows out, I think I'm almost always down, but there are lies where I can still make. Say LHO is 5=2=4=2 or 5=2=3=3 with the diamond K.
Assuming nothing interesting happens in spades at trick 2, I cross to my hand with a high trump.
If LHO shows out, I advance the diamond Q. I pretty much need LHO to hold the K since my transportation for the needed trump coup is limited
If the diamond K is onside (and of course we assume he covers), I play to elope with my trump...AJ diamonds, ruff a diamond, heart over and ruff a diamond (if rho ruffs with a spot, I pitch my heart).
If RHO shows out on the second spade, I don't even have the faint hope of a trump coup, and now have a sure trump loser, so I must find the diamond K onside and hope for an elopement...I will need LHO to be 4=2=4=3, I think.
If both follow in spades, and the 10 has appeared, I ruff a club (high by default) and lead a diamond towards my Q. RHO can't hurt me in clubs or diamonds (so long as no-one has a stiff diamond) so has to play a heart. Now I need diamonds to have been 4=3/3=4 or the short diamond to have only 2 trumps. I am then able to safely ruff the 4th diamond high, pull trump and claim.
If LHO wins the diamond K, he has to play a red card and I have to hope diamonds are splitting, but I am otherwise cold.
If spades are 3=2/2=3, and the 10 hasn't appeared, I ruff the club high and play a diamond as above.
If RHO wins, I need him to have had fewer than 5 clubs or to hold the last trump, otherwise he beats me with a club. Assuming he plays a red card, a diamond gives me the contract, so he plays a heart: I cash the diamonds and now guess a red suit. If RHO has the 3rd trump, I can't go wrong.
If LHO wins the diamond the Q, he can't lead clubs so he leads a red and I am back to needing diamonds to live and guessing a red suit to ruff to get back to my hand.
Obviously, if I knew spades were 3-2 at the outset, I'd simply ruff a club high and pull trump and claim. Catering for a 4-1 (or 5-0) break is prima facie anti-percentage, but this line has significant chances on 3-2 breaks while catering to a host of 4-1s and even 5-0's.
Figuring out the percentages is too tough for me. But this is the line that occurred to me when I first saw the problem....it takes far longer to write these things out than it does to think of them, for whatever that's worth. Having said that, it wouldn't surprise me to learn that I have over-complicated things and failed in an easy contract
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari