Heat the oil in a large casserole or very large sauté pan with a lid. Add the pancetta and sausages and sizzle for 10 minutes, turning the sausages occasionally until nicely browned and sticky. Scoop the sausages out on to a plate.

Add the onions, carrot and garlic to the pancetta and continue to cook for 3-4 minutes until the onions soften.

Return the sausages to the pan and add the rosemary, lentils, stock, vinegar and tomatoes, then season with salt and pepper. Bring to the boil and simmer rapidly for 5 minutes, then lower the heat, cover and simmer for 45 minutes, stirring every so often until the lentils are tender. (It can now be chilled and frozen for up to 1 month.).

Check the seasoning, scatter over the parsley and serve from the pan.