Place the lamb in a large nonreactive bowl and add the orange juice, vinegar and garlic. Toss to combine. Let the lamb marinate, covered, in the refrigerator for 2 hours, turning the pieces once or twice. Drain the lamb, reserving the marinade.
Heat 2 T olive oil in a flameproof casserole over medium high heat. Add the lamb, in batches, and cook until browned, about 10 minutes per batch, adding more oil as needed.
As the lamb is browned, remove the pieces to another bowl. Set the lamb aside. Reduce the heat to medium low and add the onion and carrots to the casserole. Adding more oil if necessary, cook the vegetables until softened, about 8 minutes. Then stir in the saffron, cumin, thyme, and coriander and cook over lowheat for 5 minutes to blend the flavors.
Sprinkle the flour over the vegetables and cook, stirring, for 1 minutes. Add the chickpeas, prunes, wine and reserved marinade. Season with salt and pepper.
Return the lamb to the casserole and add the tomatoes and olives. Simmer, covered over medium-low heat, stirring occasionally, for 1 1/4 hours. Stir int he lemon juice (this brightens the flavors.).
Serve over couscous, garnished with fresh mint.