The invasion and settlement of the Weald by Saxons seems to have brought a complete end to the Romano-British iron industry. No evidence of iron smelting has been found after the end of Roman rule until the ninth century when a primitive bloomery was built at Millbrook on Ashdown Forest, with a small hearth for reheating the blooms nearby. The date of this site has been established by radiocarbon and archaeomagnetic methods. The technology used there was similar to a slightly earlier furnace excavated in the eastern Netherlands, indicating that knowledge of Romano-British methods had been completely lost and replaced by the Saxons' own method. Evidence of forging of iron blooms in settlements close to the South Downs does indicate that smelting may have been going on at other undiscovered sites. It was usual for settlements concentrated along the Downs to have outlying parcels of land in the Weald for summer grazing. It is likely that smelting was carried out during the summer and the iron blooms taken back to the main settlement to work on in the winter.
In all some 30 unpowered medieval bloomery sites are known in the Weald, but most of these remain undated.  Accounts survive of the operation of just one, at Tudeley near Tonbridge in the mid-14th century.