Place the beans in a large bowl and cover generously with cold water. Cover the bowl with a plate and leave to soak for at least 8 hours or overnight. Drain the beans.
Heat the oil in a flameproof casserole dish or heavy-based saucepan and sauté the onions, carrots, celery and garlic for 5–8 minutes.
Add the water and stock together with the beans, potatoes, turnips and herbs. Bring to the boil and boil for 10 minutes.
Partly cover the casserole dish and simmer for 45 minutes or until the beans are tender. Uncover, season with the pepper and simmer for a further 10 minutes. Serve hot.