A day ahead if possible, mix the spice mixture and rub over the lamb, leave in the fridge overnight. Heat the oven to Gas Mark 5, 190°C (375°F). Remove the lamb from the fridge 20-30 minutes before cooking to allow it to get to room temperature. Place the lamb in a roasting tin and season. Add a large cup of water to the roasting tin then place, uncovered, in the oven and roast for 1¼ hours. The lamb will be cooked medium at this stage. Remove from the oven, wrap loosely in foil and allow to rest for 15 minutes before carving. Boil up the juices in the roasting tin and stir in the redcurrant jelly. Serve with the sliced lamb.
Roast some potatoes, quartered red onions and whole garlic cloves in the oven for the last 45 minutes. Steam a mixture of green vegetables, season with a little salt and black pepper and stir through a little softened butter. Other options Use the same topping on butterflied leg of lamb or butterflied new season shoulder of lamb and barbecue or roast for 40 minutes.