After 1NT, and Enemy has interfered
Show whether you are either strong, or weak but competing
The enemy's interfering bid of 2 of a suit is annoying. It means that Stayman & Transfers are off, so you've lost some flexibility, and you've lost some bidding space.
And if you bid 3, is this weak or strong ? The 2 of a suit overcall from the enemy means that the 3 bid is no longer a jump. How do you clarify this to your partner ?
And how to choose between 4-card Major and NT ?
Use Lebensohl:
- bid 3 of a suit if game is on (strong), as usual
- bid 2NT if want to get to 3 and stop (weak but competing)
- cue bid 3 of enemy suit to re-instate Stayman, but beware the level.
The 2NT is artificial. Opener must automatically bid 3 after hearing 2NT. Responder can then adjust the suit if Clubs was not his suit.
Since systems are off (Stayman & Transfers), bidding 2 of a suit is a weakness takeout.
Beware meaning of 1NT-2x-2NT reply
Of course, using Lebensohl means that the standard reply of 2NT to a 1NT opening (to show 11-12 HCP, balanced hand, or to show 12HCP balanced hand) cannot be used after interference. You and partner should be clear on this.