Complex sentence: By the 14th century Bristol was one of England's three largest medieval towns after London, along with York and Norwich, and it has been suggested that between a third and half of the population were lost during the Black Death of 1348--49.
Split into simpler sentences: By the 14th century Bristol was one of England's three largest medieval towns after London, along with York and Norwich. Between a third and half of the population were lost during the Black Death of 1348--49.