Westminster. From this point on, Royal government became increasingly centered upon Westminster, which steadily became the de facto capital. In the Middle Ages, Westminster was a small town up river from the City of London. From the 13th century onwards London grew up in two different parts. Westminster became the Royal capital and centre of government, whereas the City of London became the centre of commerce and trade, a distinction which is still evident to this day. The area between them became entirely urbanised by 1600. Trade and commerce Trade and commerce grew steadily during the Middle Ages, and London grew rapidly as a result. In 1100 London's population was little more than 15,000. By 1300 it had grown to roughly 80,000. Trade in London was organised into various guilds, which effectively controlled the city, and elected the Lord Mayor of London. Fire and plague Medieval London was made up of narrow and twisting streets, and most of the buildings were made from combustible materials such as wood and straw, which made fire a constant threat. Sanitation in London was poor. London lost at least half of its population during the Black Death in the mid-14th century. Between 1348 and the Great Plague of 1666 there were sixteen outbreaks of plague in the city. In 1666, the Great Fire gutted much of London within the city wall. References External links Medieval London.History of world cities Reassessing what we collect website – Norman London History of Norman London with objects and images A Chronicle of London from 1089 to 1483 See also History of London Britain in the Middle Ages History of London by period London