Heat the oil in a large frying pan and gently fry the chicken, onions and peppers until the chicken is browned. Stir in the flour and gradually blend in the stock.
Add the tomatoes, tomato puree, Worcestershire sauce, Italian Seasoning or Oregano, Black Pepper and salt. Stir well, cover and simmer gently for 40-50 minutes, or until the chicken is tender.