As was the case, for over a weak two, one does not take action with just an opening hand.
In direct seat, one should have the correct shape and a really good 15-count. The statement, “I had an opening hand so I had to bid” is often given as an explanation for a bad result. A hand with opening points including scattered values in the pre-empt suit should pass and wait to see if partner has the correct hand to balance. If partner cannot balance then defense is the best option. This is a much better method than bidding and finding out it is not one’s hand through a penalty double.
There are two principles to bidding in a pre-emptive auction. The first is that after partner pre-empts, he has described his hand as one-suited and any double by partner must be penalty. The second is that nobody pre-empts a pre-empt including the partner or opponents of the pre-empter. Action taken by anybody is a show of strength except a raise of the pre-empt suit which could be just furthering the pre-empt.
The bidding: East is quite happy to make a diamond pre-empt with a total of two cards in the majors. He has a six-loser hand and at equal vulnerability, he would be down two playing doubled at the three-level for -300 which is less than what opponents can get for their game.
South has a massive hand and jumps to Four Spades. This is not a pre-emptive bid. It is a stronger bid than Three Spades and shows a self-sufficient suit.
The Play: West leads the Diamond Eight and East wins the Queen and South follows with the 7. East assumes South played his lowest Diamond so he thinks that West also has the Two.
East does not want to set up Diamonds in the dummy and believes that South was not false-carding with the Diamond Seven. East exits his singleton Heart. Expecting a ruff with only a singleton trump may be wishful thinking, but it is a safe exit and if partner has the ace or if declarer takes a Heart finesse, he will ruff with a stiff trump.
A short hand ruff for the defense almost always spells disaster for the declarer.
South wins the Heart Ace and draws trump losing one Heart, one Diamond and one club, making his contract for +420.