Lionel is a contract bridge bidding convention used in defense against an opposing 1NT openings. Utilising Lionel, over a 1NT opening of the opponents:

• a double is conventional and denotes spades and a lower suit (4-4 or longer),
• a 2/2 overcall
  Overcall
  In contract bridge, an overcall is a bid made after an opening bid has been made by an opponent; the term refers only to the first such bid. A direct overcall is a bid made directly over the opening bid by right-hand opponent; an overcall in the 'last seat' is referred to as a balancing...
  
   denotes hearts and the suit bid (4-4 or longer), and
• a 2/2 overcall
  Overcall
  In contract bridge, an overcall is a bid made after an opening bid has been made by an opponent; the term refers only to the first such bid. A direct overcall is a bid made directly over the opening bid by right-hand opponent; an overcall in the 'last seat' is referred to as a balancing...
  
  s is natural.

Any of the overcalls denote high-card strength corresponding to 12+ (or good 11) high card points

Hand evaluation

In contract bridge, various bidding systems have been devised to enable partners to describe their hands to each other so that they may reach the optimum contract. Key to this process is that players evaluate and re-evaluate the trick-taking potential of their hands as the auction proceeds and...

.

The convention is named after Lionel Wright from New Zealand who published it in the International Popular Bridge Monthly magazine of May 1993.

Responses

Following the Lionel double, the partner of the double responds as follows:

(1NT) - dbl - (pass) - ??

pass = 10+ hcp, all subsequent doubles for penalty

2 = pass-or-correct bid

Pass-or-correct bid

In the card game bridge a pass-or-correct bid , is a non-forcing bid that asks partner to pass or bid differently based on her/his holding...

 (doubler to pass or bid second suit)

2 = Non-forcing

Forcing bid

In the card game contract bridge, a forcing bid is any bid that obliges the partner to bid over an intermediate opposing pass. Owing to the partnership's bidding system or a bridge convention, partner must "keep the bidding open", i.e...

, diamond length (typically 5+) with heart tolerance. Doubler can bid 2 with hearts as second suit and less than two diamonds.

2 = Natural, non-forcing

Forcing bid

In the card game contract bridge, a forcing bid is any bid that obliges the partner to bid over an intermediate opposing pass. Owing to the partnership's bidding system or a bridge convention, partner must "keep the bidding open", i.e...

2 = Weak Raise

2NT = Invitational spade raise without a singleton side suit

3// = Invitational spade raise with singleton or void in bid suit

3 = preemptive raise

After a minor suit Lionel overcall, the responses are straightforward. For instance:

(1NT) - 2 - (pass) - ??

Pass = to play

2 = to play

2 = weak raise

2 = to play

2NT = invitational heart raise

3 = preemptive

3 = preemptive

Advantages/disadvantages

Like using Brozel

Brozel

Brozel is a method for intervening against an opposing 1NT opening bid. It features the following calls:*Double – shows any single suit; advancer bids 2, after which intervenor corrects to his actual suit...

, CoCa

Comfy Canapé

In the card game bridge, CoCa or Comfy Canapé is a conventional defense against opposing 1NT openings. When playing CoCa, over a 1NT opening of the opponents, both a double as well as a 2 overcall are conventional and establish spades and hearts, respectively as anchor suits...

 or DONT

DONT

DONT is a conventional overcall against an opposing 1NT opening bid. DONT, an acronym for Disturb Opponents' Notrump, was designed by Marty A. Bergen, and is therefore also referred to as 'Bergen over Notrump'. Although the method is often criticized for being too nebulous, it remains fairly popular...

, using Lionel has the consequence of losing the penalty double over opponent's 1NT. Although this is often seen as a loss, Lionel Wright argued that this loss turns into an advantage as it opens the possibility to defend 1NT doubled with split points between you and your partner. As a balanced holding of the majority of points is far more likely to occur than holding the majority of points in an imbalanced way, a conventional non-penalty double over 1NT holds the potential of paying-off on many hands. Also, non-penalty doubles are more difficult to deal with than traditional business doubles.