Nice hand, Frances, and very well spotted
I guess you were commentating. I was playing, and since I remember the layout the problem is a bit easier.
You know the distribution in the end-position, East got 4 diamonds and 2 spades, West got a singleton diamond, 3 spades and 2 hearts.
In the actual layout, if you play the
♦9 from dummy an interesting position arise. If East raise with the A you must unblock the T, East is endplayed and must give you an entry to dummy (spade A or the free diamond-finesse). In this case you make if West got either 8 or J singleton. If East plays small you let the 9 run, felling the singleton 8. You now cash the spade A for your heart-discard and set up 2 diamond-tricks, also making.
It seems as East can succeed by a very anti-intuitive defense. If he covers the 9 with the J (from AJ52) it seems like declarer is in trouble. But declarer can counter even this, he plays a high diamond, which East must duck to deny dummy an entry. Now declarer changes tack and plays his last heart. If West wins he is forced to give declarer a dummy-entry in a major, and the 2 last diamonds can be discarded.
I was East, at my table N/S overbid to 6
♣. After a diamondlead and ruff (I returned the J, to make it clear that a heart was an unsafe return) we scored 300 (not as great a result as it looks, since our teammates went down a couple in 3NT). One reason I remembered the diamond-layout was that declarer was complaining a little about the bad breaks, and was jokingly told that at least the diamond J was finessable (there is a very social atmosphere in our premier league).
John
P 1♣ 2♦ x
3♠ 4♣ P 5♣
all pass