Wash the chickpeas, soak them overnight in 1/2 litre of water. Wash leg of lamb, dab dry, rub with oil, salt and pepper. Place in a large ovenproof dish. Chop the tomatoes in the tin with a knife. Arrange the tomatoes and chickpeas around the leg.
Peel the garlic, wash the rosemary and add to the tomatoes, season with salt and pepper. Cook in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 1 3/4 hours. In the meantime, clean and wash the spring onions, cut them into large pieces and add to the roast 15 minutes before the end of the cooking time. Serve sprinkled with coloured pepper. Serve with raw fried potatoes seasoned with rosemary