Introduction Cumulative impact zones (CIZs) are a widely used local policy to control alcohol availability in areas deemed saturated. However, there is no academic evidence of their effectiveness, and the harm associated with outlet types remains understudied. Recent alcohol policy has called for a shift towards diversified alcohol availabilitybut quantitative evidence in support of this policy is sparse. We aimed to assess whether a change in licensing policy in a London borough was associated with diversification of alcohol availability and accompanying alcohol-related violence (ARV). Method Using 11 years of local licensing data (2005/06–16/17) from the London Borough of Southwark, we measured the availability of alcohol over time by the number of extant alcohol licences (539 in 2016/17) and outlet type (drinking establishments, eateries, takeaways, off-sales, and other). We quantified harm by drawing on law enforcement intelligence that identified the incidence of alcohol-related violence against the person (deemed ARV). We analysed a linked dataset using negative binomial regression to mitigate overdispersion of data, controlling for CIZ and non-CIZ locations. Findings Across all three CIZs, implementation of the policy (in 2008 and 2009) was not associated with a change in number of licences issued. Upon disaggregation by outlet type, CIZ implementation was associated with an increase in the number of licences for eateries (incidence rate ratio [IRR] 1·58, 95% CI 1·02–2·52; p=0·04) and takeaways (3·89, 1·32–11·49; p=0·01). There was no effect on the other outlet types. Each licensed takeaway and off-sales was associated with an increase in ARV (1·7%, IRR 1·02, 95% CI 1·004–1·031; p=0·012, and 1·3%, 1·01, 1·003–1·023; p=0·008, respectively), but there was no association with drinking establishments or eateries. The other outlet type was associated with a 2·4% decrease in ARV (IRR 0·98, 95% CI 0·966–0·986; p Interpretation Although CIZ policies in Southwark have not reduced the number of licences issued, implementation has led to changes in the types of licensed outlets. We propose that takeaways and off-sales are associated with after-hours drinking and congregation. Our findings provide local stakeholders with an evidence-base for continuing to advocate licensing policy that diversifies availability. The use of law enforcement data may be biased towards areas commonly patrolled and might not capture groups who avoid police involvement (eg, gangs). Linking complementary datasets (eg, emergency department, ambulance services) would enrich the picture of alcohol-related harm. Funding None.