Method
First, heat the oven to 220°C (Gas Mark 7). Take the garlic bulb and pull it apart. Leave half of the cloves unpeeled, and peel and slice the other half. Take a large roasting dish and place the unpeeled garlic cloves in the bottom, together with three or four bay leaves and the lemon quarters. Cover them with 200ml cold water, then place the leg of lamb carefully on top. Drizzle 50ml of the oil over the lamb and rub it in well, then season generously with salt and pepper and scatter over the cinnamon. Use the point of a sharp knife to cut small slits all over the lamb skin, then push the slices of garlic and remaining bay leaves into these slits. Cover the lamb leg and its dish tightly with foil and put it into the hot oven, and immediately reduce the oven temperature to 150°C (Gas Mark 2). Cook for four hours, occasionally skimming any fat off the juices; remove the foil for the last 30 minutes’ cooking time. When the lamb has been in the oven for an hour, put the potato wedges into a separate roasting tin, then drizzle over the 4 tbsp of olive oil and season well with salt and pepper. Give everything a good turn over to ensure the potatoes are coated evenly, then put the tray into the oven to roast alongside the lamb for one and a half (or up to two) hours. When the lamb has had its time and is cooked to your liking, lift it out of its dish and wrap it tightly in foil, then leave it to rest for about 20 minutes. Have a look at the potatoes to see if they are cooked – if not, turn the oven back up to 220°C (Gas Mark 7) for 5-10 minutes while you make the sauce. Take the dish you used for the lamb and place it on the hob, then add the wine or stock and the olives, stirring well. Bring to a simmer, then keep warm until you’re ready to dish up. When the meat is rested and the potatoes are cooked, carve the lamb into thick slices and take it to the table so everyone can help themselves, together with the potato wedges and the olive sauce on the side.