1) Heat the oil in a large saucepan over a medium high heat. Brown the oxtail pieces on all sides. You may need to do this in batches. Remove and set aside. 2) Add the vegetables to the casserole and cook for 4-5 minutes, stirring occasionally. 3) Return the meat to the pan along with the herbs, peppercorns, tomato puree, wine and water. 4) Bring to the boil, then turn down to a simmer and cook for 3 – 4 hours. Until the meat is falling off the bones. 5) Remove the oxtail pieces from the stock and pull the meat from the bones. Season and cover then refrigerate overnight. 6) Strain the stock and leave to cool then leave overnight in the refrigerator as well. 7) The next day remove the layer of fat that will have formed on the top and discard. 8) Pour the remaining stock into a saucepan and bring to a simmer. Season to taste. 9) Blend the flour and three tablespoons of the hot soup in a bowl until smooth. Whisk into the soup and simmer for two minutes until thickened. 10) Add the oxtail meat to the pan and heat through until the meat is hot.