Book excerpt: It was during the later medieval period that London grew to become the largest town in the land. Certainly by the thirteenth century it had established itself as the principal port in the kingdom, head and shoulders above its rivals. The author is closely involved in a 25-year study of the London waterfront. These extensive excavations enable him to describe the changing appearance of the town and its -- with the ships and merchants over the long period from 600 to 1500. The resulting picture is a vivid reconstruction of the working port of London, the dynamic engine of the medieval economy.