Preheat the oven to 190°C/ 375°F/Gas 5. Joint the chicken, then cut it into eight pieces and set aside. Peel and chop the tomatoes and seed and slice the red peppers.
Heat half the oil in a large frying pan and sauté the onion, garlic and peppers for 3 minutes. Transfer to an ovenproof dish. Add the chicken pieces to the pan. Fry them until browned on all sides, then add them to the dish.
Add the remaining oil to the pan and, when it is hot, fry the tomatoes for a few minutes. Stir in seasoning, sugar and l tbsp (15ml) water, then spoon the mixture over the chicken. Cook, uncovered, in the oven for 30 minutes.
Remove the chicken from the oven and carefully pour the free juices from the dish into a small pan. Return the chicken to the oven and bake for 30 minutes more, covering the dish with foil if the chicken starts to get too brown.
When the chicken is almost cooked, skim the fat from the juices in the saucepan and reheat. Stir the olives into the vegetables surrounding the chicken mixture, garnish with flat leaf parsley and serve with rice. Pour the pan juices into a jug and pass round as extra gravy.