Worldwide there are 350 million people with chronic hepatitis B infection and globally it causes up to half of the liver cancer deaths and one third of deaths from cirrhosis. Only a fraction of sufferers will develop these complications. Various studies have implicated socio-demographic, biochemical and viral factors in disease progression but research has been limited to local populations in endemic countries. Our aim was to study the prevalence and factors associated with advanced disease of hepatitis B infection in immigrants living in East London. I completed a retrospective analysis of notes and electronic health records of 1209 immigrant patients attending hospitals in East London, 217 of whom were from Bangladesh and Pakistan. Screening of volunteers attending local mosques using oral mucosal transudate swabs and national statistics data allowed us to calculate prevalence rates in these populations. Those 13 patients from Bangladesh and Pakistan admitted over 30 months with decompensated disease were men aged > 40. Age, sex, ALT, smoking, alcohol and diabetes were significant predictors for cirrhosis and decompensated disease but not viral markers. Similar analyses were performed for other ethnicities with similar outcomes. The scale of under diagnosis of hepatitis B for all ethnicities was estimated and the reasons explored. This work has scrutinised the epidemiology of chronic hepatitis B in East London and the difficulties encountered exploring it. We provide differing results to published studies and suggestions for how this domain can be examined further.