1) In a large frying pan, gently heat 2 tablespoons of oil. Fry the sausages for 30 minutes, turning when necessary, until brown and sticky on all sides. 2) Meanwhile, fry the onions, garlic, carrots and celery for 3-4 minutes in the remaining 3 tablespoons of oil. 3) Add the tinned tomatoes, mixed herbs, and season to taste. Cover and simmer for 30 minutes. 4) Cut each sausage into 3 pieces and add to the casserole with the beans. Simmer for a further 10 minutes.