Soak the beans overnight in a saucepan of cold water. The next day, drain them, rinse well and return to the pan. Cover with water, bring to the boil and simmer for 1 hour. Skim off any froth that rises to the top during cooking. Drain and set aside.
Heat the oil in a large saucepan and cook the bacon for 5 minutes until golden. Add the onions, garlic, carrot and celery, and gently saut