Process
The Romans imported a whole variety of materials: beef, corn, glassware, iron, lead, leather, marble, olive oil, perfumes, purple dye, silk, silver, spices, timber, tin and wine. The main trading partners were in Spain, France, the Middle East and North Africa.
Britain exported lead, woollen products and tin. In return, it imported from Rome wine, olive oil, pottery and papyrus. British traders relied on the Romans to provide security within the Empire. When this collapsed and Europe was seemingly overrun by Barbarians, no one could guarantee traders that their produce would get through. Also, without the power of Rome, who would be willing to buy what was produced in Britain and other parts of Europe?