Bolted on to our one-level opening system (which is Acol), we use a variant of Lucas Twos. It is compliant with the EBU's Level Two (for novice events) but is not well-known.  We have found it crops up roughly twice an evening in a session of 24 boards.

2♠  is our strong, artificial bid, which promises either 23+ points balanced or a hand of 4 losers or fewer.  It says nothing about our spade holding.  2NT is our relay response, whatever responder holds.

2♣ , 2♦  and 2♥  are all weak, natural openings, promising 4+ cards in the suit bid and 5-9 HCP and either a second suit or 6 cards in the suit opened.  If opener has a two-suited hand, his second suit may be longer or shorter than the suit opened, but he will have 9+ cards in the two suits.  

• Responses: 2NT is a strong and forcing. On the other hand, the next bid up — i.e. 2♣:2♦, 2♦:2♥,  and 2♥:2♠ — is a non-forcing weak response promising 3+ cards in the suit bid. 

We call these two-level openings 'antispades' because you cannot immediately show a normal Weak Two in spades.

One possible defence to the three weak opening bids is as follows:

• Double with 16+ points and any shape, or 11-15 points and tolerance for each of the other three suits.
• 2 of a New Suit shows a good 6+ card or very good 5-card suit, along with 7 losers or fewer.
• 2NT shows a two-suited hand in any of the three unbid suits, 6 losers or fewer.
• 3 of a New Suit shows a good 6+ card suit or very good 5-card suit, along with 6 losers or fewer.

Gavin and Kay 8-SEP-17