Step 1: Preheat the oven to 220C.

Step 2: Toss the onion and celery with a little of the olive oil in a roasting pan, then roast for 20 minutes until caramelised. Dry roast the walnuts on a baking tray in the oven for 6 minutes, then rub their skins off with a clean tea towel and set aside.

Step 3: Toss the meat in flour seasoned with salt and pepper, shaking off the excess.

Step 4: In a heavy-based frying pan, brown the oxtail in batches in the remaining olive oil and the butter over high heat. Transfer each batch to a large heavy-based casserole.

Step 5: Deglaze the frying pan with the wine, scraping to release all the caramelised bits from browning. Add the garlic, onions, celery, herbs and tomatoes to the frying pan and reduce the wine a little over high heat, then tip everything into the casserole. Add the beef stock and the water, making sure that everything is immersed, and simmer over low heat, covered, until tender – this could take 3 to 4 hours.

Step 6: Add the orange rind and olives in the last 20 minutes of cooking.

Step 7: Strain the cooking juices from the meat and skim as much fat as possible from the top. Set the meat aside in a warm place.

Step 8: In a stainless steel or enamelled saucepan, combine the Red Wine Vinegar and sugar and boil until the vinegar has evaporated and the sugar has caramelised.

Step 9: Reduce the cooking juices to a syrupy consistency, then add the caramelised vinegar mixture to taste.

Step 10: Toss the cooked oxtail with the walnuts and pour the sauce back over the oxtail. Serve with mashed potato, creamy polenta or pasta.