The importance of bidding game when you can and how pre-empting can disrupt the bidding.

East has a horrid weak 2♦ - thought the vulnerability is the most favourable.

Over a pass South will bid 1♥ 

West could try a weak jump overcall with 3♣ which now makes it difficult for N/S to find their best contract of 4♠ s.

North will probably double to show the other suits and values.

If East supports ♣ s, South will bid 4♥ as partner is likely to be short in ♣ s.

If East passes South has a difficult bid - 3 or 4♥ .

One partnership bid 4♥ , the other 2 in 3♥ s were split, with one making the correct 11 tricks.