Historically it was assumed to be a radius of approximately 5 miles from St Mary-le-Bow church in Cheapside. This area would have included neighbourhoods such as Shoreditch, Bethnal Green, Hackney, and parts of Poplar and Stepney. However, urban development and noise pollution mean that the bells can't be heard that far today. It's also worth noting that in 2012, experts from the University of London conducted a study and found that the bells could only be heard approximately 2 miles away. However, this study was conducted in modern conditions, with all the noise pollution of a busy city.