Remove the lamb from the packaging and pat dry. Cover and set aside.
Cook the cous cous according to directions but add a stock cube and cinnamon to the water. Mix well. Let stand for 10-15 minutes. Add the other cous cous ingredients and mix through. Cover and refrigerate.
Make the dressing by putting the remaining ingredients, except the figs and parsley, in a large jar and shaking well to mix into a thick creamy dressing. (If the tahini is too thick, you can let down the dressing by adding a little hot water).
Preheat the BBQ to high. Season the lamb with salt and pepper. Cook each side for 5 minutes each side. Reduce heat to medium-low and cook, covered, for 10 minutes for medium. Transfer to a plate and cover with foil. Set aside for 15 minutes to rest.
To serve, cover a very large serving platter with the couscous salad. Carve the lamb and serve on the couscous. Separate the fat from the cooking juices and pour the cooking juices over the lamb. Dress the dish with the tahini dressing.
