Heat the oil in a large saucepan. Add the onion, carrots, leek, bacon and garlic and cook gently over a low heat for 5 minutes, stirring often until softened.
Add the stock, bay leaf and parsley sprigs and bring to a gentle boil. Add a good pinch of salt, cover, reduce the heat and cook gently for 10 minutes.
Stir in the tomato paste, kidney beans and macaroni, bring back to a gentle boil and cook for another 10 minutes, stirring often to prevent the pasta from sticking. Add the green beans after 5 minutes.
When the macaroni is cooked, remove the bay leaf and parsley, then taste to check the seasoning. If you like, serve garnished with sprigs of flat-leaf parsley.