Jennbridge: A Successful Gambit

I was playing at Roy Hoppe's club with Dave Neuman today.  Dave made an imaginative bid that worked well.  He dealt and held, with neither side vulnerable:

♠  AKQTxx
♥  AJ
 ♦  Kx
♣  Jxx

He bid 1 Spade.  LHO overcalled 2 Clubs.  I passed.  RHO advanced 2 Diamonds.  Back to him.  What would you do?

Dave eschewed such mundane bids as 2 or 3 Spades.  Instead, he chose to bid 3 Diamonds!  Dave and I have an agreement that when the opponents have bid two suits, a cue bid of one of them shows a stopper in that suit but not the other.  So he showed a diamond stopper and asked me to bid 3NT with a club stopper.  While it is true that this would only produce the eighth trick if spades ran, he decided to go for it since I might have something else useful that would produce another.  I held

♠  xxx
♥ T98
♦  QJx
♣ Q9xx

Not much, but when they didn't find the potentially killing heart lead, it was enough.  RHO played the ten to my queen, so the 9 was a second stopper.  If he instead won it with the king, there was no defense (hearts cannot be led from his side without setting up 2 tricks in the suit).   I only needed to play a diamond and that was 9 tricks (spades were 3-1).  I actually made ten, since when I led a diamond, LHO went up with the ace and I unblocked the king.   (If he ducked, there would only be 9 since I wouln't be able to set up another diamond and untangle all the tricks.)  +430 was a cold top.  +400 would have still been a top; everybody else was in 3 or 4 Spades.

Good luck!