An important 15th century source throws light on the organisation of what was one of medieval England's wealthiest ports. In 1200 the Suffolk town of Dunwich was one of medieval England's wealthiest ports. However, a succession of marine inundations in the late thirteenth and early fourteenth centuries drastically reduced its size and importance. Evocative descriptions of Dunwich's long struggle against the sea abound, but little has been written about the medieval town itself. The Bailiffs' Minute Book of 1404-30 is the single most substantial and informative document to have survived from the borough's medieval archive. It provides new insights into the town's bitter legal dispute with neighbouring Walberswick, its system of government and the men who administered and financed the town.Of even greater importance are the many references to the fortunes and organisation of the fishing industry. Additionally, the Minute Book contains a number of detailed tax assessments, thus revealing how local communitiesshared the burden of royal lay subsidies. These assessments are among the first of their kind to be published. Mark Bailey is High Master of St Paul's School, and Professor of Later Medieval History at the University ofEast Anglia.