Season the chicken with salt and pepper. Heat oil in a heavy bottomed saucepan over medium-high heat. Cook chicken and sausage separately in hot oil until well browned on both sides. Reserve browned chicken and sausage.
Turn the heat to low. Make the roux by melting 30g of margarine into the oil in the pan. Sprinkle the flour over the oil and margarine and cook, stirring constantly, until roux turns a nutty brown, about 10 minutes.
Melt the remaining 50g margarine into the roux. Stir in the onion, garlic, green pepper and celery; cook for 10 minutes. Add the Worcestershire sauce, 4 tablespoons chopped parsley and salt and pepper to taste. Cook, stirring often for an additional 10 minutes.
Pour the hot water into the pan and add the stock cubes, chicken and sausage. Bring to the boil, reduce heat and simmer for 45 minutes before stirring in the tomatoes and okra. Cover pan and simmer for 1 hour. Stir in spring onions and prawns and top with 2 tablespoons chopped parsley before serving.