Heat the oil in a flameproof casserole dish over a medium heat. Sauté the beef until it is just cooked, then remove and keep to one side. Sauté the carrots, onions and tomatoes in the same pan for a few minutes, stirring continuously to prevent sticking.
Blend in the flour using a wooden spoon, and cook for a few more minutes. Return the cooked mince to the casserole.
Cover the mixture with the hot stock, and simmer the soup gently for about 45 minutes. Serve hot.