Trim the chicken joints neatly and dip both sides in seasoned flour. Add to the hot butter melted in a frying pan. Fry the chicken joints gently, turning to brown on both sides. Then lift from the pan and place in a casserole.
Peel and slice the onions and halve, deseed and shred the green peppers. Add these to the hot butter remaining in the frying pan. Cover and fry gently for about 10 minutes to soften them.
Meanwhile skin the tomatoes, then halve them and scoop out the seeds. Chop the tomato flesh up coarsely and add to the chicken joints along with the softened onion and green peppers. Season with salt and pepper and add the sugar. Add the stock. Cover the casserole with a lid, place in the centre of a moderate oven (180°C., 350 °F., Gas Mark 4) and cook for 1 hour. Serve the chicken joints with the cooked vegetables and juices from the casserole.