Leave the lentils to soak overnight in a large pot full of water. The next day change the water, add salt and bring to the boil over high heat. Drain the lentils and set to one side.
Fry onion in a large pot with a little oil till translucent. Add the bacon and fry till browned.
Add celery, leek, garlic, carrots and potatoes.
Add sausages and wine, tomatoes, bay leaves and lentils.
Cover and cook till the potatoes and lentils are soft, about 20 minutes. Check if there is enough liquid about halfway through cooking and add a little water if necessary. Remove bay leaves, season with pepper, no more salt, as the bacon and sausage will likely make the stew salty enough.