The sale of factory-made cigarettes with menthol as characterising flavour has been prohibited in Great Britain since May-2020. However, menthol accessories like flavoured filters for roll-your-own (RYO) tobacco can be sold legally, possibly undermining the policy. This study aimed to explore the association of RYO and menthol cigarette smoking. Data were collected between October-2020 and October-2023 from a monthly population-based cross-sectional survey, with 82,120 adults (18+) living in Great Britain providing complete data. Logistic regression models assessed the association between predominant RYO tobacco use and menthol cigarette smoking, and whether it differed by sociodemographic characteristics, unadjusted and adjusted for age, gender, ethnicity, nation, and socioeconomic position. Time-trends in RYO tobacco use among people smoking menthol cigarettes were modelled over the study period. There has been no clear decrease in menthol cigarette smoking prevalence among people who smoke (~14%) following the ban. Predominant RYO use increased among people smoking menthol cigarettes from 49.6% (95%CI: 42.2-57.0) in October-2020 to 61.9% (95%CI: 57.5-66.0) in June-2022, after which it remained stable. Predominant RYO use was more common among people smoking menthol than non-flavoured cigarettes overall (adjusted odds ratio (ORadj)=1.30, 95%CI: 1.14-1.49) and across demographic subgroups. This association was most pronounced in middle-aged compared with older people (35 vs. 65 years ORadj=1.18, 95%CI: 1.01-1.35), and in ethnic minorities compared with White people (ORadj=1.56, 95%CI: 1.03-2.36). There was a substantial increase in RYO use among people smoking menthol cigarettes in the first two years after the ban, from approximately 50% to 60%. The availability of menthol accessories may have undermined the ban on factory-made mentholated cigarettes in Great Britain. Roughly one in seven people who smoke cigarettes still report smoking menthol cigarettes and among these, about two thirds predominantly use roll-your-own tobacco. Since there has been no noteworthy change in the prevalence of menthol cigarette smoking since October-2020, new measures will likely be necessary to achieve a further reduction. For example, menthol accessories could be banned or their advertising and availability heavily restricted.