cheese is Caerphilly, named in 1831 but made long before that. Originally a method for storing excess milk until it could be brought to market, it was a moist cheese that would not last very long. Production of the cheese was halted due to milk rationing after World War II, although it was still made in England. There, the cheese was produced very quickly and sold early in its maturation process, creating a dryer cheese. In the 1970s, production of Caerphilly returned to Wales and over the following few decades a variety of new cheeses have also been produced in Wales. Cereals As far back as the Iron Age, Welsh folk were using wild cereals to create a coarse bread. By the time the Romans invaded, Celtic skills with bread had progressed to the point that white or brown breads could be produced. The Roman invasion led to many Welsh people moving to the less hospitable uplands, where the only cereal crops which could be grown were oats, barley and rye. Oat and barley breads were the main breads eaten in Wales up until the 19th century, with rye bread created for medicinal purposes. Oats were used to bulk out meat or meat and vegetable stews, also known as pottage. The Welsh also created a dish called llymru, finely ground oatmeal soaked in water for a long time before boiling until it solidified. This blancmange-styled dish became so popular outside Wales that it got a new name, flummery, as the English could not pronounce the original. A similar dish, sucan, was made with less finely ground oatmeal, making a coarser product. Vegetables Celtic law made specific provision with regard to cabbages and leeks, stating that they should be enclosed by fences for protection against wandering cattle. The two green vegetables were the only ones mentioned specifically in the laws, though uncultivated plants were still likely to be used in their cooking. The leek went on to be so important to Welsh cuisine—found in many symbolic dishes including cawl and Glamorgan sausage—that it became the country's national vegetable. Potatoes were slow to be adopted amongst Welsh folk, despite being introduced to the UK in the 16th century; only in the early 18th century did they become a Welsh staple, due to grain failures. Once the potato did become a staple, it was quickly found in Welsh dishes such as cawl, and