In 1199 King John made Dunwich a free borough, a status that allowed it considerable control over its own affairs and its own borough officers. Dunwich was given a charter and a seal. One hundred years later the town was awarded two members of parliament. The museum has an excellent medieval collection. There you can see pots like these, a sherd of fine imported ware, jewellery, a purse hanger and coins: things used in everyday life by the citizens and merchants of the rich medieval town. There is also the brooch with a mysterious inscription worn by a lady. Because of St Felix, Dunwich at this time was a prominent destination for pilgrims. The port also made it an excellent point of embarkation for the important sites on the Continent. The museum has a fine collection of pilgrim items like this lead bottle for holy water, and brooches and clips.
Medieval Dunwich had eight churches and a Knights Templar church. The Dominicans (Blackfriars) and Franciscans (Greyfriars) both had monasteries. Because the town was so full the Greyfriars had to build outside the ramparts and their ruins survive. There was a leper hospital (next to the present church) and the Maison Dieu hospital (now the car park). The 13th century was the golden era for Dunwich. It was one of the ten largest towns in England, high in the estimation of the crown. It was rich, ecclesiastically and politically important. The sea had created a fine deep water harbour.
But the tides were still coming from the north, bringing with them thousands of tons of sand and shingle, twice a day. On three nights early in 1286 a huge storm raged, sweeping away the lower parts of the town and joining the spit of land to the coastline to the south of the town. Dunwich no longer had a harbour. Channels were dug through the shingle to enable some maritime access to the town but in 1328 an even fiercer storm, causing great loss of life, finally blocked the harbour. The Blyth and Dunwich rivers forced their way to the sea between Walberswick and Southwold. Dunwich went into a slow decline.