Dunwich was becoming a thriving port despite the ravages of Viking raids. The sea, all the time, was changing the coast, producing a safe haven protected by the encroaching spit of land to the north. In the 11th century William the Conqueror, a Norman (themselves descendants of Vikings), marched into Britain and in 1086 he ordered a survey of his new kingdom. This was the Domesday Book, which is kept at the National Archives in Kew. Dunwich rated a long and detailed entry, part of which reads:
'Edric of Laxfield held Dunwich before 1066 as one manor; Twenty Four Frenchmen with 40 acres of land. Burgesses 236, poor men 180, They pay 4 10s. The land on the cliff used to be 200 acres, as the Sea had carried off the other 100'
This was an early mention of coastal erosion, the factor that was to destroy the town. But at this time the erosion, coupled with the growing spit of land, was creating a near perfect harbour, where ships from the Continent could be safe from gales. Dunwich was a boom town. Ships brought wine from France, alum from Spain, flax from Prussia, and salt from Gascony. Cheese was exported as was wool, to the low countries where it was woven into cloth and brought back to England, via Dunwich.The markets would have bustled with cosmopolitan crowds: merchants, farmers, tradesmen, officials, clerics and pilgrims. The fishing trade was at the heart of Dunwich’s prosperity and part of its debt to the Crown was paid in barrels of herrings.