Background By measuring alcohol retailers’ propensity to illegally sell alcohol to young people who appear highly intoxicated, we examine whether UK legislation is effective at preventing health harms resulting from drunk individuals continuing to access alcohol. Methods 73 randomly selected pubs, bars and nightclubs in a city in North West England were subjected to an alcohol purchase test by pseudo-drunk actors. Observers recorded venue characteristics to identify poorly managed and problematic (PMP) bars. Results 83.6% of purchase attempts resulted in a sale of alcohol to a pseudo-intoxicated actor. Alcohol sales increased with the number of PMP markers bars had, yet even in those with no markers, 66.7% of purchase attempts resulted in a sale. Bar servers often recognised signs of drunkenness in actors, but still served them. In 18% of alcohol sales, servers attempted to up-sell by suggesting actors purchase double rather than single vodkas. Conclusions UK law preventing sales of alcohol to drunks is routinely broken in nightlife environments, yet prosecutions are rare. Nightlife drunkenness places enormous burdens on health and health services. Preventing alcohol sales to drunks should be a public health priority, while policy failures on issues, such as alcohol pricing, are revisited.