Removing the max bet button from a slot's interface cut the share of stakes placed at £10 or more by 22% after 11pm, according to a twelve-week trial run across four UK-licensed operators and published this month by the Gambling Commission's research unit. The drop was measured against a control group of players on identical games where the button stayed in place, and it held after adjusting for session length and time of day. The effect was concentrated almost entirely in the 11pm–3am window; during daytime hours the same change moved high-stake share by less than 3%.

The trial covered 18,400 accounts and roughly 2.1 million spins across three high-variance slots and one medium-variance game, all with a £10 maximum stake. Players in the treatment arm saw the stake selector default to £1 with a manual entry field, but no single-tap shortcut to the ceiling. Nobody was blocked from staking £10 — they simply had to type it.

What the trial actually changed

The intervention was deliberately narrow. No deposit limits were altered, no session timers added, no messaging shown. The only difference between arms was the presence or absence of a one-tap button setting the stake to the game's maximum.

That matters for how you read the result. A 22% reduction in high-stake share is not the same as a 22% reduction in money lost. The researchers tracked stake distribution, not net loss, and they were explicit about the limitation. What they can say is that the friction of typing a number, rather than tapping a button, was enough to shift behaviour for roughly one in five high-stake spins late at night.

The time-of-day split is the more interesting finding. Between 7am and 7pm, high-stake share fell 2.6% in the treatment arm — within noise for a sample this size. Between 11pm and 3am it fell 22%. The researchers' working hypothesis is that late-night players are more likely to be operating on autopilot, and autopilot behaviour is exactly what a max bet button is designed to serve.

Why the button exists at all

It is worth being clear-eyed about the commercial logic. The max bet button is not a player-protection feature, and it is not really a convenience feature either. On high-variance slots it exists to let a player chase a loss or press an advantage quickly, and it is disproportionately used by players who have already decided to stake at the ceiling. Operators have resisted removing it because a small share of players account for a large share of handle, and those players notice friction.

The trial's own data hints at this. In the treatment arm, the mean number of spins per session rose 4.1% — players staking less per spin played slightly longer. Handle was down 6.8% overall, but gross gaming yield was down only 2.3%, because the mix shifted toward lower-variance, higher-margin play. That is a smaller revenue hit than operators might fear, though the trial was not powered to detect GGY effects reliably and the authors say so.

The 11pm cliff

The concentration of the effect after 11pm is not a fluke of this sample. It lines up with what we already know about late-night play: sessions that start after 11pm run longer, involve more re-deposits, and are more likely to be flagged by operator harm-prevention teams. The Commission's own 2023 prevalence data put the peak hour for "at-risk" play at 11pm–1am, and the number of accounts gambling past midnight on weekdays has risen steadily since 2021.

If friction works hardest when players are least deliberate, then the max bet button is doing its damage precisely when it does the most harm. That is a cleaner argument for removal than any aggregate figure.

The counter-argument

There is a reasonable objection, and it comes from players rather than operators. A player who wants to stake £10 and has to type it every time will find the interface annoying, and annoyed players do one of two things: they leave, or they find a workaround. The trial did not measure workarounds, but the researchers note that manual entry fields are a known vector for fat-finger errors — a player meaning to type £1.00 and hitting £10.00 by accident. The treatment arm logged 340 stake-entry corrections over the trial, against 12 in the control. Most were caught before the spin, but not all.

There is also the question of whether hiding a button is meaningfully different from a hard cap. If the policy goal is to reduce late-night high-stake play, a £5 cap after 11pm would achieve it more directly and more transparently. The counter-counter is that caps are blunt and push players to other operators; friction is soft, deniable, and keeps the player on-site. Whether that is a feature or a bug depends on your view of how much a regulator should be shaping behaviour through interface design rather than rules.

What happens next

The Commission has not signalled a policy position, and it would be a mistake to read the trial as a precursor to a ban. What it has done is hand operators a number they cannot easily dismiss: 22% at 11pm, for the cost of one button.

Three of the four participating operators have since made the change permanent on their highest-variance titles. The fourth has not, and declined to comment on the record. That asymmetry is worth watching — if friction is genuinely effective, it becomes a competitive disadvantage to keep the button, and a competitive advantage to be seen removing it. If it is not, the operators who kept it will quietly out-earn the ones who didn't, and the next trial will be harder to run.

The open question is not whether hiding the button works. It is whether an intervention this small — one tap, one typed number — is the right place to draw the line, or whether it is a comfortable substitute for the harder measures the late-night data keeps pointing toward. The 11pm cliff did not appear because of a button. The button just happened to be standing on it.