This deal is from an EBU online duplicate.
After South had opened one diamond and West overcalled one heart North doubled to show four spades. This was not the partnership agreement, North had forgotten that double showed less than four spades. South had remembered and so assumed there was no spade fit and bid what he hoped he could make.
West led a small heart, declarer played the jack from dummy as he wanted to be there to take the spade finesse. After the ten of spades held declarer was able to run the spades with West throwing small hearts. Now declarer cashed the diamonds, carefully starting with a top honour from hand so that he could pick up four one breaks with a singleton ten or jack in either hand. After cashing the diamonds it was clear that West had come down to Kx in hearts and some high club honours. South played a club, with West holding both top honours there was nothing the defence could do, West cashed his clubs and had to lead away from the heart king at trick twelve. Making eleven tricks in notrumps was a complete top, as everyone else had played in spades, usually making ten or eleven tricks.