Photograph: Martin Poole
Preheat the oven to 180°C, fan 160°C, gas 4. Toast the pine nuts in a frying pan until golden, then set aside. Fry the onion in the olive oil for about 8 minutes until it's softened and golden.
Meanwhile, wilt the spinach in a large lidded pan then tip into a colander and press out the excess moisture.
Unroll the lamb on a chopping board, fat-side down, and season lightly. Mix the spices, raisins, spinach and pine nuts with the onion and cook for 1-2 minutes. Spoon evenly across the lamb then re-roll and tie to secure. Place the lamb joint in a roasting tin and roast for 65 minutes (25 minutes per 500g plus 25 minutes) for medium well or 20 minutes per 500g, plus 20 minutes if you prefer it pink, basting occasionally. Rest for 10-15 minutes before carving. The lamb will tend to fall apart as you carve it, rather than cutting into neat slices, but that's all part of the rustic charm!
Serve the roast lamb with chilli butternut squash roasted around the lamb, and giant couscous.
Get ahead: the stuffing can be made and the lamb stuffed in advance, but cool the stuffing before spreading it over the lamb.