Acol Bidding System: Weak Notrump and Four-Card Majors

Acol is the natural bidding system of British bridge. Its two trademarks are a weak 1NT opening of 12-14 points and four-card major openings: you may open 1♥ or 1♠ with only four cards, and partner raises with four-card support.

Everything else follows from those two choices. Balanced hands of 15-19 open one of a suit and show their strength with a notrump rebid, raises are limit raises, and the two-level openings come in three flavors: old-style strong Acol twos, weak twos with a strong 2♣, or Benjamin twos. If you learned 2/1 or SAYC, the middle of an Acol auction will feel familiar. The first two rounds will not.

Acol takes its name from the Acol Bridge Club on Acol Road in Hampstead, north-west London, where a group of players built the system in the early 1930s. Terence Reese credited Maurice Harrison-Gray, Jack Marx and S. J. Simon as the main designers. The first book on it, The Acol Two Club by Ben Cohen and Terence Reese, came out in 1938, and Iain Macleod (later better known as a politician) did a lot to spread it.

The founders wanted a system built on judgment rather than rules: open light, limit your hand early, and let partner decide. That spirit is still there. Acol has fewer artificial bids than most modern systems, and many of its sequences are natural and non-forcing.

Today the English Bridge Union teaches a version called Standard English Acol (first published in 1996 as "Standard English"). It is the default at clubs across England, Scotland and Wales. Sit down with a stranger at a British club and the first question is usually "Acol, weak no trump?"

Most Acol players open light hands with good shape. Many use the Rule of 20: add your high card points to the length of your two longest suits, and open if the total is 20 or more.

The 1NT opening is the core of Acol. It shows 12-14 high card points and a balanced hand: 4-3-3-3, 4-4-3-2 or 5-3-3-2. Many pairs also allow a five-card major in the 5-3-3-2 shape, so ask your partner.

Why open so light? Frequency and pressure. We counted every possible 13-card hand: a balanced 12-14 (4-3-3-3, 4-4-3-2 or 5-3-3-2) is about 9.7% of all hands, a balanced 15-17 about 4.9%. So the weak notrump appears about twice as often as the strong one. Each time it does, the next player has to come in at the two level, often without knowing whether their side has a fit, while your side has described its hand in one bid.

Responses to a weak 1NT:

The arithmetic is simple. Game in notrump needs about 25 points, so responder invites with 11-12 and bids game with 13 or more. That is three points more than opposite a 15-17 notrump, and it is the first adjustment a 2/1 or SAYC player has to make. Traditional Acol uses the weak takeouts above; if you prefer Jacoby transfers, they work just as well over a weak notrump. To compare the ranges, see what a 1NT opening means in Acol and four other systems.

The price of the weak notrump is the penalty double. When the next player doubles 1NT with 15 or more and your side holds only 18-21 points between you, 1NT doubled can go two or three down.

Every Acol partnership needs an escape agreement, often called a "wriggle". The common basics: with a weak hand and a five-card suit, responder runs to it; with a weak balanced hand, responder uses a redouble or a pass to start a search for the cheapest playable fit, depending on your methods. Agree yours before the first round, not after the first -500.

With 15 or more and a balanced hand, you open one of a suit and show your range on the rebid. Modern Acol uses these ranges:

Older books used 15-16 for the 1NT rebid and 17-18 for 2NT, with 19 shown by a jump to 3NT. Many club players still use those numbers, so check.

This is the mirror image of Standard American. There, a 1NT rebid shows 12-14 and the strong balanced hands open 1NT. In Acol the 12-14 hands open 1NT and the 15-17 hands rebid it. Both work, as long as you and partner know which one you play.

Acol opens your longest suit. With five cards in one suit and four in another, open the five-card suit. With two four-card suits, the English Bridge Union's teaching advice is short: with exactly four hearts and four spades open 1♥, otherwise open the higher-ranking suit. Older books gave other rules, so it is worth a word with a new partner.

Because a 1♥ or 1♠ opening may hold only four cards, the raises promise four-card support:

With three-card support and 6-9 points, responder usually bids 1NT or a new suit first and supports later if it still matters. The same logic applies to opener: a 1♠ response promises only four spades, so opener raises it only with four-card support. You can check what the 1♥ - 2♥ raise promises in Acol and in the five-card major systems.

Two reasons. First, they find 4-4 major fits at once: you open 1♥ with four, partner has four, partner raises, done. Second, the weak notrump takes out the balanced 12-14 hands, so a one-of-a-suit opening is usually either shapely or 15+. That makes it safe to open a four-card major.

The cost is real but small. Responder cannot raise on three-card support, so some 5-3 fits are found a round later, and a major suit opening tells the opening leader less about the suit.

North has a balanced 15 count with four hearts. That is outside the 12-14 range, so North opens 1♥, planning to rebid 1NT (15-17) over a 1♠ response. South has 10 points and four hearts, the exact hand for a limit raise to 3♥. North has more than a minimum and goes on to 4♥. The two hands hold 25 points, the usual amount for game.

In 2/1 or SAYC, North would open 1NT and South would need Stayman to find the same fit. In Acol the four-card major opening finds it at once, and East and West never get a cheap chance to come in.

The two-level openings are where Acol players differ most. You will meet three styles:

1. Traditional Acol twos. 2♦, 2♥ and 2♠ are strong and forcing for one round: a good six-card suit (or two five-card suits) and about eight playing tricks. 2♣ is the only game force, normally 23+ points. Responder's 2NT is the negative reply to an Acol two.
2. Strong 2♣ with weak twos. 2♣ covers every strong hand. 2♦, 2♥ and 2♠ are weak twos: a good six-card suit and about 6-10 points. This is the direction English Bridge Union teaching has taken.
3. Benjamin twos. Devised by Albert Benjamin of Glasgow. 2♣ shows the old Acol two: a strong hand about one trick short of game, usually with a long suit (many versions also put a balanced range just above 2NT here). 2♦ is the game force, including the very big balanced hands. 2♥ and 2♠ are weak twos. Responder answers 2♣ with a 2♦ relay, and many pairs use 2♥ as the negative reply to 2♦.

"Benjamin Acol" just means Acol with Benjamin twos. It keeps weak twos in both majors and still has a home for the big one-suiters, which is why so many club players adopt it.

Acol itself is the openings and the response ranges. The conventions on top are mostly the ones everybody uses:

• Stayman over 1NT and 2NT.
• Weak takeouts or transfers over 1NT. Traditional Acol uses weak takeouts; many modern pairs play red-suit transfers.
• Blackwood or Roman Key Card Blackwood for slams.
• Fourth suit forcing when responder needs a forcing bid with no natural one.
• Negative doubles, called "Sputnik" in older British books.
• Checkback after opener's notrump rebid, so responder can find a 5-3 major fit.
• Gerber over notrump openings, and a Baron 3♣ over 2NT in many partnerships.
• A weak notrump escape (the wriggle described above).
• Michaels cue bids and the Unusual 2NT in competition.

None of these is unique to Acol. Each one is a tool you can add or drop as a partnership.

The biggest adjustment for an American player is the notrump. The hands you open 1NT in Acol are the ones you open with a minor and rebid 1NT in SAYC, and the other way round. For a British player moving to 2/1, the shock is the five-card majors and the forcing 1NT response. For the bigger picture, see five-card majors vs four-card majors and weak notrump vs strong notrump.

Strengths

• The weak notrump is frequent and awkward to compete against.
• Limit bids come early, so most hands are described in two bids and partner can judge.
• Four-card majors find 4-4 fits immediately.
• It is natural and easy to learn, with few alerts.

Weaknesses

• 1NT can be doubled for penalty, and an escape system is needed.
• Balanced 15-19 hands open one of a suit, which lets the opponents in cheaply.
• Raises need four-card support, so some 5-3 major fits are found late.
• If you play strong Acol twos, you give up weak twos in the majors.

Acol is the standard system at British clubs and in English Bridge Union teaching, so most people who learned bridge in England, Scotland or Wales learned Acol first. You also meet it in Ireland and among players who learned the game in Britain, and several bridge apps offer Acol robots.

At the top level the picture is mixed. Many British internationals play strong notrump or strong club systems, but the weak notrump is still part of plenty of expert methods because it works so well at pairs. For the openings of each system side by side, see bridge bidding systems compared, and for how a bidding system works in general, the bridge bidding system guide.

A summary gets you halfway; the rest comes from bidding hands. In the Bidding Room on BridgeDummy you choose one system for your side and one for the opponents, and Acol is one of the five on the list. You sit South, a robot partner sits North and bids Acol, and you can tap any robot call to see what it meant. When the auction ends, your contract and the other contracts you could have reached are solved double dummy on up to 20 layouts that fit the bidding, so you see the average score of each one and whether your 2NT invitation or your limit raise was right. The robots' Acol card plays a 12-14 notrump with four-card majors and weak twos, the version you meet at most British clubs.

A simple plan for your first week:

1. Bid 20 deals with Acol for your side and SAYC or 2/1 for the opponents.
2. Before each 1NT, check the range: 12-14 opens 1NT, 15-17 opens a suit and rebids 1NT.
3. After each auction, look at the deals where your contract scored below the best one and ask which bid gave the wrong picture.

Stuck on a call in a real game? Enter your hand and the auction on the What Should I Bid page and choose Acol: it suggests the next call and tells you what it means.