Heat the oil in a large frying pan, add the onion and cook over a medium heat for 5 minutes until softened. Add the red pepper, carrot, potato and garlic, if using, and cook for a further 5 minutes. Stir in the spice mix, tomatoes, sugar, stock and plenty of salt and pepper and bring to the boil.
Stir the kidney beans into the pan and bring to the boil, then cover and simmer for 45 minutes until the vegetables are tender.
Add the green vegetables, re-cover and simmer for 5 minutes until just cooked. Serve with crusty bread.