Wash the beans, boil the stock or water. Soak the beans in the stock or water all night. Chop the bacon and slice the vegetables. Melt the fat in a deep pan and fry very gently the bacon, onion, celery, turnip and potato for 10 min. Add the water or stock, beans, herbs and mace; bring all to boiling-point and simmer for 2 hr. or until the beans are quite soft. Remove the herbs, sieve the vegetables and stir the milk into the purée. No starch thickening, other than the potato, should be needed. Reheat and season.