Cut the lamb into thumb-sized cubes. Spike the flour with a teaspoon of sea salt and black pepper. Toss the lamb cubes in the seasoned flour.
Heat a large pan and pour in 2 tablespoons of olive oil. When the oil starts to smoke, add as many lamb pieces as will fit in one layer, cover with a lid and cook for a few minutes until soft and browned evenly. Remove from the pan, then repeat with the remaining cubes until they are all browned. Return all the lamb to the pan and turn the heat down.
Add the onion, celery, garlic, cinnamon, walnuts and bay leaves to the pan. Put the lid back on and cook very gently for 3 to 5 minutes, stirring often to make sure nothing sticks to the bottom of the pan, until the onion is softened.
Cut your pomegranates in half and ease out a few of the seeds and put to one side. Juice them as you would an orange or lemon. You should end up with about 500ml of juice. (If you can't find pomegranates, shop-bought cranberry juice works well instead.) Stir the juice into the lamb and top up with water to cover. Simmer very gently for 1½ hours, or until the lamb is tender, adding a little water now and then if the stew gets dry.
Remove and discard the cinnamon stick and bay leaves. Season to taste and sprinkle with the parsley and reserved pomegranate seeds. Lovely served with steaming hot saffron rice.