Heat the oven to 190c/fan 170c/gas 5. Trim any excess fat from the oxtail. Season well and dust with a little flour. Heat 5 tbsp oil in a large casserole or roasting tin, add the oxtail and brown all over. Lift out, then repeat with the bacon, before returning the oxtail and any juices to the pan.
Tie the carrots, leek, celery and herbs tightly in a bundle with kitchen string and add it to the meat with the wine. Bring to the boil, scraping up any bits stuck to the bottom, then pour in the stock and cover with a double layer of baking parchment.
Cook in the oven for 4 hours, until the meat is soft and falling off the bone. Serve with mash.