Pat the lamb shanks with kitchen paper and season. Heat 2 tbsp oil in a large ovenproof pan. Once the oil is hot, add the lamb and brown the meat on all sides. Remove from the pan, add the rest of the oil, followed by the carrots, onions and garlic. Once the onions and garlic are soft, add the sage and anchovies. Return the lamb to the pot and add the tomatoes. Refill the tin with water and add that to the pot with the wine. Cover and cook in the oven at 180C/Gas Mark 4 for 2½ hours, removing the cover after 2 hours and adding the olives.