Heat the oil in a large, heavy-based saucepan in which the sausages fit in a single layer. Add the sausages and cook over a medium heat for 10–12 minutes until golden brown all over. Remove and set aside.
Add the onion and celery to the pan and cook over a low heat for 8–10 minutes until softened. Stir in the garlic and cook for a further 2 minutes.
Increase the heat to high, pour in the wine and boil vigorously for 2 minutes, scraping any sediment from the base of the pan. Stir in the tomatoes, stock, bay leaf and chilli and bring to the boil. Add the lentils and return the sausages to the pan. Simmer gently for 40 minutes, or until the sausages and lentils are cooked through. Season with salt and pepper. Serve with a drizzle of extra virgin olive oil, accompanied by some crusty bread.