Trim fat off lamb. Cut meat into 4 cm chunks. In a 5-6 quart pan, combine lamb, onion, garlic, ginger, turmeric, and saffron. Cook, tightly covered, over medium heat for 30 minutes. Meanwhile, in a bowl combine vinegar and 1 litre water. Trim off stems, tough outer leaves, and sharp tips of artichokes, leaving pale, tender interior leaves. Cut in half lengthwise; scoop out and discard hairy chokes. As artichokes are trimmed, immerse in vinegar-water. After meat cooks 30 minutes, turn heat high, uncover pan, and stir often until juices evaporate and meat browns, 15-20 minutes. Stir in 2 cups water; simmer, covered, for 1 hour. Drain artichokes and add to lamb; simmer, covered, for 20 minutes. Add 8 preserved lemon quarters and olives; simmer, covered, until artichokes are tender when pierced, about 10 minutes longer. Add 2 tablespoons liquid from preserved lemons or lemon juice. Skim and discard fat from stew. Pour stew into a bowl and garnish with remaining lemon quarters.