Preheat the oven to 190 C / 375 F / 170 FAN / Gas 5.
Peel the onion and cut into wedges, quarter the mushrooms, cut the peppers and courgette into 2cm pieces.
Place the vegetables on a large roasting dish and drizzle over 1 tablespoon of the oil and season with the salt and pepper.
Place the sausages in the smaller roasting dish with the remaining oil, making sure that they are well spaced out.
Roast the vegetables and sausages for 30 minutes, turning after 15 minutes.
While everything is cooking peel and finely chop the shallot and garlic.
Place the chopped garlic, shallot and bacon lardons in the frying pan and cook over a medium heat for a few minutes until softened.
Slice the tomatoes in half and add to the pan with the tomato purée and the flour.
Stir to combine and cook for a minute.
Add the stock and stir until thickened.
Add the beans, mixed herbs and salt and pepper until hot.
Serve, with the vegetables mixed with the beans and the sausages.