Heat the oil in a large frying pan, add the chicken and onions, frying in batches if needed for 5 minutes until golden.
Stir in the garlic, then mix in the flour. Add the stock, lemon rind and juice, saffron, cinnamon and plenty of seasoning and bring to the boil. Transfer to a tagine or casserole dish. Add the chickpeas and potatoes, mix together, then cover. Cook in a preheated oven, 180°C (350°F), Gas Mark 4, for 2 hours.
Stir, then sprinkle with the herbs. Spoon into shallow bowls and serve with warm pitta breads.