First make the stuffing. Peel and core the apples, slice thinly and put into a saucepan with the lemon juice, sugar and ginger. Cook over a gentle heat until the apples are just soft, then set aside to cool. . Preheat the oven for 200ºC . Trim the lamb, remove the skin and score the fat. Lay the joint out on a board, fat side down. Spoon the apple mixture along the center. Roll up and tie with twine. Peel the garlic and cut it into slivers, then pierce the joint all over with the point of a sharp knife and slip the slivers of garlic into the pockets formed. Season with the salt and pepper, put the joint in a roasting pan and cook in the hot oven for 30 minutes, then heat the cider in a small pan and pour it over the lamb. Reduce the heat to moderate (350F) and cook for another 40 minutes, basting frequently. When the lamb is cooked, put it onto a heated serving dish and keep warm. Remove any excess fat from the pan juices, boil up over a high heat until reduced slightly, and serve with the sliced lamb.