ACES on bridge
I would expect East to pass as dealer here, then double at his second turn to speak. If South could redouble to show a strong hand, there is something to be said for that action, after which East would retreat to two diamonds. Now 300 is available by doubling this, but at most forms of scoring, there is a lot to be said for aiming higher, since if you bid three no-trump and make it, the rewards are far greater.
At many tables, East would unthinkingly win the first diamond and try to cash the suit from the top. That would make sense if South had a doubleton diamond, but how likely is that? Not very, I’d say.
East does best to duck the first or second diamond, stopping the easy route home via the club finesse. Declarer has a counter: He must run the hearts, forcing East to make two discards. The first one, a small spade, is easy; the second appears relatively innocuous as well, in that he must throw an apparently irrelevant small club. But then declarer has to reconstruct the hand. Since East appears to have started with four spades, two hearts and five diamonds, he either has the bare club king or doesn’t. South must cash the club ace and exit with his remaining diamond. East is now endplayed; he can cash his diamonds but in the three-card ending he must lead into dummy’s spade tenace and concede the rest.
ANSWER:
Reluctant as I am to lead my readers into bad habits, in third seat at any form of scoring or vulnerability, I’d be unwilling to pass here. With a good suit I know what I want partner to lead, so I feel obligated to open one diamond. It may not work out, but the negative inferences from my failing to act are almost as important as the positive ones. Partner will never play me for a good suit if I pass here.