Put the chicken into a large roasting tin and drizzle with 2 tablespoons of the oil. Mix the crushed seeds, chillies, oregano and cinnamon with some salt and pepper, then sprinkle half over the chicken.
Cover the chicken loosely with foil, then roast in a preheated oven, 190°C (375°F), Gas Mark 5, for 40 minutes. Remove the foil and baste with the pan juices. Add the potatoes to the tin, toss in the juices, then cook uncovered for 40–50 minutes, basting and turning the potatoes once or twice until golden brown. Re-cover the chicken with foil if the spice rub begins to overbrown.
Meanwhile, heat the remaining oil in a small saucepan, add the shallots and garlic, if liked, and fry for 5 minutes until softened. Stir in the remaining spice rub and cook for 1 minute. Cook the green beans in a saucepan of boiling water for 5 minutes, then drain and toss in the shallot mixture with the lemon juice.
When the chicken is cooked (see