Using a pestle and mortar or a mini chopper, mash or chop the garlic with a generous pinch of salt, then add the lemon juice, ras el hanout spice mix and olive oil, then pound or chop to a rough paste. Use a small knife to make small incisions all over the lamb. Sit the lamb in a large, shallow casserole dish or deep roasting tin, then rub the paste all over the lamb and into the cuts. Leave at room temperature for 1 hr, or better still, cover and chill overnight.

When ready to cook, heat the oven to 160C/140C fan/gas 3. Scatter the onion wedges around the lamb, then cover the dish with a lid or tightly with foil and roast for 3 hrs. Remove from the oven and uncover. Stir the onions and baste the lamb in the juices, then turn the oven up to 180C/160C fan/gas 4 and continue to roast the lamb, uncovered, for 25-30 mins until browned.

Lift the lamb and onions onto a board to rest and put the kettle on. Stir the couscous and raisins into the lamb dish so they’re coated in the roasting juices. Pour over enough boiling water from the kettle to just cover the couscous, then cover the dish and leave for 5 mins. Uncover and fluff the couscous up with a wooden spoon, then stir through the chickpeas, chopped herbs and preserved lemon or lemon juice, and season to taste. Bring the lamb, onions and the couscous to the table to serve.