The French even-money rules that almost halve your house edge, when the casino is honest about offering them.
Editorial illustration for the lesson on la partage and en prison, in the Mayfair Casino School.
La Partage and En Prison
Annabel Cavendish
Editor · 14 May 2026
Why Zero Is the Whole Problem on Even-Money Bets
On a European single-zero wheel, the even-money bets (red, black, odd, even, 1-18, 19-36) cover 18 of the wheel's 37 pockets. You win when your colour, parity, or range comes in. You lose when the other 18 numbers come in. The zero is the point: it belongs to neither group. When zero lands on an even-money bet, without any French rule in place, the casino takes your stake. Zero lands on average 1 time in 37 spins. That single pocket is the entire source of the 2.703% edge on even-money bets.
La Partage and En Prison both address what happens at that one pocket. They change the zero outcome from a full loss to a partial or deferred loss. The difference between the two rules is procedural rather than mathematical: La Partage gives you half back immediately, En Prison gives you a second chance to recover all of it on the next spin. La Partage is cleaner and faster. En Prison is marginally worse in expected value but provides the possibility of full recovery, which some players prefer as an experience.
La Partage: The Arithmetic
The French word "partage" means sharing or division. The rule is exactly that: when zero lands, the even-money bet is divided. Half goes to the casino, half returns to the player. The expected loss per spin changes as follows. Without La Partage: you lose 1 unit when zero lands (probability 1/37), so the contribution of zero to expected loss is 1/37 = 2.703%. With La Partage: you lose only 0.5 units when zero lands, so the contribution of zero is 0.5/37 = 1.351%. The edge on La Partage even-money bets is exactly half the standard European edge.
This calculation is simple enough to carry in your head. If you're playing red/black and zero lands, you get half your chips back. The mathematical consequence is that the casino is collecting 1.351% of every even-money bet you place rather than 2.703%. That's not a trivial difference. At £100 per spin on red, 50 spins per hour, the hourly expected cost drops from £135 to £67.50. Over a four-hour session, that's £270 saved, which at Mayfair table limits represents meaningful money across a year of regular play.
En Prison: The Deferred Recovery
En Prison, "in prison" in French, works differently. When zero lands, your even-money stake is locked in place for the next spin. You don't win anything and you don't lose anything yet. On the next spin, if your original bet wins, your stake is returned to you: no profit, but full stake recovery. If your original bet loses on that spin, the casino takes the imprisoned stake. If zero lands again on the imprisonment spin, the rules vary by venue: some apply a second imprisonment, some return half the stake (effectively applying La Partage to the imprisonment).
The expected edge on En Prison is approximately 1.39%, marginally higher than La Partage at 1.351%. The mathematical reason: the imprisoned bet rides at full 2.703% wheel odds on its recovery spin, including the possibility of landing zero again and extending or losing the imprisonment. La Partage settles immediately at 50% loss, which is a slightly better expected outcome than riding the recovery spin at the full edge. The difference (1.39% versus 1.35%) is small enough that a typical session won't reveal it. But the direction is clear: La Partage is marginally preferable in expected value terms.
The Casino de Monte-Carlo's grande table, where French roulette operates with a €5 minimum and €2,000 maximum per bet, offers both La Partage and En Prison as options when zero lands, per the Casino de Monte-Carlo's published table games information. The player chooses. At a UK venue offering both, La Partage is the rational selection unless you have a specific reason to prefer the chance of full stake recovery.
Where to Find These Rules in London and Online
The practical landscape in London is straightforward to navigate, but you need to ask directly. La Partage is not a default condition at every European single-zero table; it's an additional rule that some venues apply and others don't. Aspers Westfield Stratford applies La Partage on its European tables, making it the best standard edge available on a UK land-based casino floor for even-money play. Other London venues run European single-zero tables without La Partage, charging 2.703% on even-money bets.
En Prison is rarely encountered in standard London play. Most UK venues that offer French rules use La Partage, because it settles in one step and is operationally simpler for the croupier and the pit. En Prison requires tracking imprisoned stakes across the subsequent spin, which creates administrative complexity and slows the game. Online, En Prison is essentially unavailable at live dealer tables. Evolution, Playtech, and Pragmatic Play all implement La Partage where they offer a French rule, per their published product specifications. The UKGC's published standards for casino game rules permit either rule at licensee discretion, but La Partage is the universal online standard.
The Session-Level Calculation
The difference between 2.703% and 1.351% is not academic at real stakes. At £50 per spin on red, playing 50 spins per hour at a London venue for a four-hour session: total wagered is £10,000. At 2.703%, expected loss is £270. At 1.351%, expected loss is £135. The saving over that single session is £135. Across a year of monthly four-hour even-money sessions at that stake: £135 per session saved, twelve sessions, total saving approximately £1,620. The saving grows in direct proportion to stake and frequency. At £200 per spin, the annual saving is over £6,000 compared to playing the same sessions on a European table without La Partage. The sessions feel identical; the expected annual cost is substantially different. This is why confirming La Partage before you sit down is one of the most practically useful things you can do, and why asking the pit or floor staff which rule applies to their even-money bets on this table is a question worth asking.
Key numbers
Rule
What happens when zero lands
Edge on even-money bets
Edge on inside bets
Standard European
Full stake lost
2.703%
2.703%
La Partage
Half stake returned immediately
1.351%
2.703%
En Prison
Stake locked; recovered if next spin wins
~1.39%
2.703%
American (no French rule)
Full stake lost (0 and 00)
5.263%
5.263%
Annabel
0:000:00
Welcome to the lesson on La Partage and En Prison.
I'm Annabel, and these are the two French roulette rules that genuinely do make a mathematical difference to what you're paying at the table.
Not a large difference, but a real and calculable one, and knowing when they apply, and when they emphatically don't, is one of the more practically useful pieces of knowledge in this series.
Let me start with why the house edge exists on even-money bets.
You lose if any of the eighteen black numbers comes up.
The zero is the point.
There are thirty-seven pockets and you're being paid as though there are thirty-six.
That one extra pocket, zero, is the entire source of the two point seven percent house edge.
On even-money bets, it lands against you roughly one time in thirty-seven.
La Partage changes what happens when zero lands.
Instead of losing your entire stake, you receive half of it back.
Exactly half the standard European edge.
En Prison does something slightly different.
When zero lands, your stake is locked, imprisoned, for the next spin.
If your bet wins on that spin, you receive your stake back with no profit.
If it loses, the casino keeps it.
The mathematics of En Prison produces an edge of approximately one point three nine percent, marginally worse than La Partage because the imprisoned bet rides at the full two point seven percent wheel odds, including the possibility of hitting zero again.
La Partage is unambiguously better in expected value terms.
The difference is small enough that you'd need a large number of sessions to notice it, but the direction is clear.
Here is the thing I most need you to know about both rules: they apply exclusively to even-money bets.
Red and black, odd and even, low and high, the first and second eighteen.
They do not apply to dozens.
They do not apply to columns.
They do not apply to street bets, corners, splits, or straight-ups.
This is the most common misconception among players who move to a French table thinking they are now paying one point three five percent on all bets.
A player who moves to a French table and then bets a dozen is paying the standard European rate, regardless of the French designation.
The rule halves the impact of the zero only on those bets.
Now: where do you actually find these rules?
The SBM website confirms this is the only venue within the SBM group offering genuine French roulette.
At that table, if zero lands, the player may choose between La Partage and En Prison, both being offered as options.
French-style rules on the French Riviera are the historical norm at licensed French casinos, though the national gambling authority does not mandate them.
They are a traditional commercial practice.
In London, the situation is considerably less generous.
The UKGC does not mandate La Partage.
It is entirely a commercial choice, and most UK floors, even those running single-zero European wheels, do not offer it.
Aspers at Westfield Stratford is one of the few confirmed exceptions: their European tables apply La Partage publicly, reducing the even-money edge to one point three five percent.
This is verified.
For a serious player who cares about edge and doesn't require a Mayfair postcode, that matters.
Online, the rules are more consistently available, precisely because they're commercially straightforward to implement.
Evolution's French Roulette Gold and the Pragmatic Live French Roulette table, which was added to the live dealer catalogue in mid-2025, both apply La Partage on even-money bets as standard.
Playtech's French Roulette table does the same.
On these tables, the rule is automatic: zero lands, half your even-money stake returns, no theatre required.
En Prison is essentially unavailable at online live dealer tables because it's operationally impractical when multiple players at the same table have bets at different stages of imprisonment.
La Partage is the universal online standard because it's a one-step settlement.
The reason La Partage isn't universally offered at UK land-based casinos comes down to margin.
It halves the casino's theoretical revenue on even-money bets.
No regulation requires them to offer it, and most operators don't volunteer to halve their take.
If you want it, you need to find a French table specifically, and most mid-tier UK venues don't have one.
One practical note for anyone planning a trip.
At one hundred pounds per bet, fifty bets per hour, a hundred hours of play across a year, the difference in expected loss is six thousand seven hundred and fifty pounds.
That is not trivial.
It is worth asking.
La Partage and En Prison are not a strategy.
They don't make roulette a winning game.
That is all.
But on those bets, it's the best available edge the house will give you at a live table.
