Heat the oil in a large heavy pan or heatproof casserole. Add the onions and fry for about 5 minutes, stirring occasionally, until they are lightly browned.
Stir in the lamb and fry for about 10 minutes until browned. Stir in the rice until all the grains are glistening.
Break the cinnamon stick in half, if using. Stir the cinnamon and oregano into the rice with the stock, Worcestershire sauce, tomatoes, salt and pepper.
Stir well, then bring to the boil. Cover and simmer for 15 minutes until the rice is tender and stock is absorbed.
Just before serving, stir in the parsley.
