Hi all
We’re at the end of the match, pretty much drained after 60something boards. One of the last deals could have had a nice twist if I had kept my eye on the ball. Not that it would have changed the outcome, though.
1
1. Standard weak two
Geoff leads the Jack, and this is what I see.
The Ace is played in dummy and in a pipe dream moment I pitch my 2 … discouraging a switch. Declarer follows up with a to his Queen and Geoff’s Ace. Suddenly the defence is an open book to me. A to me, cashing both King & Ace, a ruff and then the cream on the cake with a third round of promoting my Ten into the setting trick.
Now if only I hadn’t played that 2 in trick one. Geoff returns a trump for dummy [let declarer clean up his own mess] and ten tricks get wrapped up easily with a 
hook.
So can declarer prevent the promotion of the Ten?
It looks a bit counterintuitive, but if declarer starts with a top from dummy [retaining the Queen in his hand], my Ten wouldn’t get a toxic payload.
I agree, trump to the Queen by me at trick two was not my finest moment… But not for the reason described: the way cards lie contract is safe. When in the end North attempts to promote South’s Ten, dummy ruffs high and draws the last trump of defense (K-J were still present in trumps).
However, high trump from dummy at trick two is still better for two reasons: South might have all four missing trumps (having 5=4=2=2) or (more likely) North on top of stiff spade might hold ATx in trumps and manage to get TWO spade ruffs.
Wait, I take it back. Dummy still has a third diamond. So my play was bad for THREE different reasons. :-)